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	$54.27	7.416%	$58.2947	$58.29	$58.30	$58.30
Purchase #2	$141.28	4.741%	$147.9781	$147.98	$148.00	$148.00
Purchase #3	$139.57	3.413%	$144.3335	$144.33	$144.35	$144.30
Purchase #4	$109.39	3.387%	$113.095	$113.10	$113.10	$113.10
Purchase #5	$244.46	9.407%	$267.4564	$267.46	$267.45	$267.50
Purchase #6	$233.30	6.218%	$247.8066	$247.81	$247.80	$247.80
Purchase #7	$32.27	3.765%	$33.485	$33.49	$33.50	$33.50
7 purchase totals =	$954.54		$1,012.4493	$1,012.46	$1,012.50	$1,012.50