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	$118.92	10.489%	$131.3935	$131.39	$131.40	$131.40
Purchase #2	$208.73	6.528%	$222.3559	$222.36	$222.35	$222.40
Purchase #3	$33.76	9.786%	$37.0638	$37.06	$37.05	$37.10
Purchase #4	$99.43	11.812%	$111.1747	$111.17	$111.15	$111.20
Purchase #5	$140.31	3.599%	$145.3598	$145.36	$145.35	$145.40
Purchase #6	$209.60	9.456%	$229.4198	$229.42	$229.40	$229.40
Purchase #7	$46.67	3.316%	$48.2176	$48.22	$48.20	$48.20
7 purchase totals =	$857.42		$924.9851	$924.98	$924.90	$925.10