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	$209.64	5.332%	$220.818	$220.82	$220.80	$220.80
Purchase #2	$7.37	4.309%	$7.6876	$7.69	$7.70	$7.70
Purchase #3	$128.63	12.521%	$144.7358	$144.74	$144.75	$144.70
Purchase #4	$96.92	4.813%	$101.5848	$101.58	$101.60	$101.60
Purchase #5	$53.57	7.248%	$57.4528	$57.45	$57.45	$57.50
Purchase #6	$187.88	10.146%	$206.9423	$206.94	$206.95	$206.90
Purchase #7	$95.64	10.147%	$105.3446	$105.34	$105.35	$105.30
7 purchase totals =	$779.65		$844.5659	$844.56	$844.60	$844.50