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	$62.68	8.651%	$68.1024	$68.10	$68.10	$68.10
Purchase #2	$99.73	11.772%	$111.4702	$111.47	$111.45	$111.50
Purchase #3	$35.38	3.804%	$36.7259	$36.73	$36.75	$36.70
Purchase #4	$165.37	13.772%	$188.1448	$188.14	$188.15	$188.10
Purchase #5	$33.84	8.713%	$36.7885	$36.79	$36.80	$36.80
Purchase #6	$119.92	9.360%	$131.1445	$131.14	$131.15	$131.10
Purchase #7	$235.86	7.398%	$253.3089	$253.31	$253.30	$253.30
7 purchase totals =	$752.78		$825.6852	$825.68	$825.70	$825.60