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	$88.94	11.162%	$98.8675	$98.87	$98.85	$98.90
Purchase #2	$165.52	4.488%	$172.9485	$172.95	$172.95	$172.90
Purchase #3	$10.63	12.284%	$11.9358	$11.94	$11.95	$11.90
Purchase #4	$145.33	11.185%	$161.5852	$161.59	$161.60	$161.60
Purchase #5	$180.91	12.837%	$204.1334	$204.13	$204.15	$204.10
Purchase #6	$187.73	12.734%	$211.6355	$211.64	$211.65	$211.60
Purchase #7	$171.76	4.717%	$179.8619	$179.86	$179.85	$179.90
7 purchase totals =	$950.82		$1,040.9678	$1,040.98	$1,041.00	$1,040.90