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	$165.97	3.185%	$171.2561	$171.26	$171.25	$171.30
Purchase #2	$61.54	4.245%	$64.1524	$64.15	$64.15	$64.20
Purchase #3	$130.82	11.507%	$145.8735	$145.87	$145.85	$145.90
Purchase #4	$215.86	13.338%	$244.6514	$244.65	$244.65	$244.70
Purchase #5	$191.33	13.367%	$216.9051	$216.91	$216.90	$216.90
Purchase #6	$172.91	6.163%	$183.5664	$183.57	$183.55	$183.60
Purchase #7	$151.56	4.790%	$158.8197	$158.82	$158.80	$158.80
7 purchase totals =	$1,089.99		$1,185.2246	$1,185.23	$1,185.15	$1,185.40