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	$93.68	6.515%	$99.7833	$99.78	$99.80	$99.80
Purchase #2	$97.50	8.617%	$105.9016	$105.90	$105.90	$105.90
Purchase #3	$139.83	13.807%	$159.1363	$159.14	$159.15	$159.10
Purchase #4	$226.43	4.713%	$237.1016	$237.10	$237.10	$237.10
Purchase #5	$152.91	5.465%	$161.2665	$161.27	$161.25	$161.30
Purchase #6	$68.98	4.585%	$72.1427	$72.14	$72.15	$72.10
Purchase #7	$244.98	12.695%	$276.0802	$276.08	$276.10	$276.10
7 purchase totals =	$1,024.31		$1,111.4122	$1,111.41	$1,111.45	$1,111.40