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	$221.54	8.175%	$239.6509	$239.65	$239.65	$239.70
Purchase #2	$56.88	9.468%	$62.2654	$62.27	$62.25	$62.30
Purchase #3	$168.32	3.551%	$174.297	$174.30	$174.30	$174.30
Purchase #4	$231.54	4.415%	$241.7625	$241.76	$241.75	$241.80
Purchase #5	$71.45	5.188%	$75.1568	$75.16	$75.15	$75.20
Purchase #6	$59.59	7.865%	$64.2768	$64.28	$64.30	$64.30
Purchase #7	$71.58	10.164%	$78.8554	$78.86	$78.85	$78.90
7 purchase totals =	$880.90		$936.2648	$936.28	$936.25	$936.50