Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$142.62	4.415%	$148.9167	$148.92	$148.90	$148.90
Purchase #2	$101.90	7.709%	$109.7555	$109.76	$109.75	$109.80
Purchase #3	$170.42	6.514%	$181.5212	$181.52	$181.50	$181.50
Purchase #4	$142.41	11.229%	$158.4012	$158.40	$158.40	$158.40
Purchase #5	$105.25	3.279%	$108.7011	$108.70	$108.70	$108.70
Purchase #6	$213.91	3.562%	$221.5295	$221.53	$221.55	$221.50
Purchase #7	$148.69	11.588%	$165.9202	$165.92	$165.90	$165.90
7 purchase totals =	$1,025.20		$1,094.7454	$1,094.75	$1,094.70	$1,094.70