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	$165.63	13.516%	$188.0166	$188.02	$188.00	$188.00
Purchase #2	$225.29	3.483%	$233.1369	$233.14	$233.15	$233.10
Purchase #3	$114.75	13.759%	$130.5385	$130.54	$130.55	$130.50
Purchase #4	$92.57	5.173%	$97.3586	$97.36	$97.35	$97.40
Purchase #5	$154.61	12.553%	$174.0182	$174.02	$174.00	$174.00
Purchase #6	$28.77	13.862%	$32.7581	$32.76	$32.75	$32.80
Purchase #7	$191.27	4.323%	$199.5386	$199.54	$199.55	$199.50
7 purchase totals =	$972.89		$1,055.3655	$1,055.38	$1,055.35	$1,055.30