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	$81.75	11.287%	$90.9771	$90.98	$91.00	$91.00
Purchase #2	$53.67	3.697%	$55.6542	$55.65	$55.65	$55.70
Purchase #3	$158.47	13.124%	$179.2676	$179.27	$179.25	$179.30
Purchase #4	$114.26	7.673%	$123.0272	$123.03	$123.05	$123.00
Purchase #5	$195.28	13.246%	$221.1468	$221.15	$221.15	$221.10
Purchase #6	$192.44	12.463%	$216.4238	$216.42	$216.40	$216.40
Purchase #7	$152.79	4.760%	$160.0628	$160.06	$160.05	$160.10
7 purchase totals =	$948.66		$1,046.5595	$1,046.56	$1,046.55	$1,046.60