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	$53.70	10.489%	$59.3326	$59.33	$59.35	$59.30
Purchase #2	$136.84	4.418%	$142.8856	$142.89	$142.90	$142.90
Purchase #3	$73.59	7.833%	$79.3543	$79.35	$79.35	$79.40
Purchase #4	$65.50	8.466%	$71.0452	$71.05	$71.05	$71.00
Purchase #5	$207.39	10.755%	$229.6948	$229.69	$229.70	$229.70
Purchase #6	$194.70	4.112%	$202.7061	$202.71	$202.70	$202.70
Purchase #7	$155.75	8.422%	$168.8673	$168.87	$168.85	$168.90
7 purchase totals =	$887.47		$953.8859	$953.89	$953.90	$953.90