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	$228.73	10.415%	$252.5522	$252.55	$252.55	$252.60
Purchase #2	$70.70	3.359%	$73.0748	$73.07	$73.05	$73.10
Purchase #3	$57.82	13.654%	$65.7147	$65.71	$65.70	$65.70
Purchase #4	$156.77	6.736%	$167.33	$167.33	$167.35	$167.30
Purchase #5	$64.89	10.398%	$71.6373	$71.64	$71.65	$71.60
Purchase #6	$98.79	12.408%	$111.0479	$111.05	$111.05	$111.00
Purchase #7	$87.27	7.732%	$94.0177	$94.02	$94.00	$94.00
7 purchase totals =	$764.97		$835.3746	$835.37	$835.35	$835.30