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	$94.88	3.531%	$98.2302	$98.23	$98.25	$98.20
Purchase #2	$159.82	3.414%	$165.2763	$165.28	$165.30	$165.30
Purchase #3	$207.53	10.412%	$229.138	$229.14	$229.15	$229.10
Purchase #4	$83.77	7.501%	$90.0536	$90.05	$90.05	$90.10
Purchase #5	$178.79	4.840%	$187.4434	$187.44	$187.45	$187.40
Purchase #6	$174.33	12.717%	$196.4995	$196.50	$196.50	$196.50
Purchase #7	$172.53	12.383%	$193.8944	$193.89	$193.90	$193.90
7 purchase totals =	$1,071.65		$1,160.5354	$1,160.53	$1,160.60	$1,160.50