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	$147.56	5.566%	$155.7732	$155.77	$155.75	$155.80
Purchase #2	$92.92	4.468%	$97.0717	$97.07	$97.05	$97.10
Purchase #3	$68.98	3.293%	$71.2515	$71.25	$71.25	$71.30
Purchase #4	$209.53	12.402%	$235.5159	$235.52	$235.50	$235.50
Purchase #5	$119.95	3.320%	$123.9323	$123.93	$123.95	$123.90
Purchase #6	$180.85	5.272%	$190.3844	$190.38	$190.40	$190.40
Purchase #7	$38.98	4.612%	$40.7778	$40.78	$40.80	$40.80
7 purchase totals =	$858.77		$914.7068	$914.70	$914.70	$914.80