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	$56.64	3.483%	$58.6128	$58.61	$58.60	$58.60
Purchase #2	$174.98	3.131%	$180.4586	$180.46	$180.45	$180.50
Purchase #3	$185.95	3.415%	$192.3002	$192.30	$192.30	$192.30
Purchase #4	$109.65	13.687%	$124.6578	$124.66	$124.65	$124.70
Purchase #5	$191.31	4.633%	$200.1734	$200.17	$200.15	$200.20
Purchase #6	$108.41	5.416%	$114.2815	$114.28	$114.30	$114.30
Purchase #7	$121.47	8.463%	$131.75	$131.75	$131.75	$131.80
7 purchase totals =	$948.41		$1,002.2343	$1,002.23	$1,002.20	$1,002.40