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	$91.58	7.262%	$98.2305	$98.23	$98.25	$98.20
Purchase #2	$151.42	5.399%	$159.5952	$159.60	$159.60	$159.60
Purchase #3	$77.98	6.296%	$82.8896	$82.89	$82.90	$82.90
Purchase #4	$162.67	10.419%	$179.6186	$179.62	$179.60	$179.60
Purchase #5	$149.46	11.765%	$167.044	$167.04	$167.05	$167.00
Purchase #6	$172.78	5.204%	$181.7715	$181.77	$181.75	$181.80
Purchase #7	$165.73	13.503%	$188.1085	$188.11	$188.10	$188.10
7 purchase totals =	$971.62		$1,057.2579	$1,057.26	$1,057.25	$1,057.20