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	$68.27	9.659%	$74.8642	$74.86	$74.85	$74.90
Purchase #2	$158.36	4.132%	$164.9034	$164.90	$164.90	$164.90
Purchase #3	$194.31	13.833%	$221.1889	$221.19	$221.20	$221.20
Purchase #4	$71.90	9.708%	$78.8801	$78.88	$78.90	$78.90
Purchase #5	$89.59	7.346%	$96.1713	$96.17	$96.15	$96.20
Purchase #6	$239.38	7.275%	$256.7949	$256.79	$256.80	$256.80
Purchase #7	$92.70	11.439%	$103.304	$103.30	$103.30	$103.30
7 purchase totals =	$914.51		$996.1068	$996.09	$996.10	$996.20