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	$94.31	9.104%	$102.896	$102.90	$102.90	$102.90
Purchase #2	$30.83	7.655%	$33.19	$33.19	$33.20	$33.20
Purchase #3	$48.72	10.722%	$53.9438	$53.94	$53.95	$53.90
Purchase #4	$90.28	10.715%	$99.9535	$99.95	$99.95	$100.00
Purchase #5	$195.88	7.324%	$210.2263	$210.23	$210.25	$210.20
Purchase #6	$245.88	9.601%	$269.4869	$269.49	$269.50	$269.50
Purchase #7	$210.69	13.674%	$239.4998	$239.50	$239.50	$239.50
7 purchase totals =	$916.59		$1,009.1963	$1,009.20	$1,009.25	$1,009.20