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	$102.80	9.289%	$112.3491	$112.35	$112.35	$112.30
Purchase #2	$86.95	7.461%	$93.4373	$93.44	$93.45	$93.40
Purchase #3	$198.51	7.659%	$213.7139	$213.71	$213.70	$213.70
Purchase #4	$145.68	13.764%	$165.7314	$165.73	$165.75	$165.70
Purchase #5	$223.73	6.623%	$238.5476	$238.55	$238.55	$238.50
Purchase #6	$101.31	10.413%	$111.8594	$111.86	$111.85	$111.90
Purchase #7	$119.69	11.458%	$133.4041	$133.40	$133.40	$133.40
7 purchase totals =	$978.67		$1,069.0428	$1,069.04	$1,069.05	$1,068.90