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	$165.99	4.715%	$173.8164	$173.82	$173.80	$173.80
Purchase #2	$52.90	6.215%	$56.1877	$56.19	$56.20	$56.20
Purchase #3	$243.53	8.473%	$264.1643	$264.16	$264.15	$264.20
Purchase #4	$220.72	10.234%	$243.3085	$243.31	$243.30	$243.30
Purchase #5	$182.73	7.260%	$195.9962	$196.00	$196.00	$196.00
Purchase #6	$55.29	6.847%	$59.0757	$59.08	$59.10	$59.10
Purchase #7	$161.94	10.842%	$179.4975	$179.50	$179.50	$179.50
7 purchase totals =	$1,083.10		$1,172.0463	$1,172.06	$1,172.05	$1,172.10