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	$98.48	6.843%	$105.219	$105.22	$105.20	$105.20
Purchase #2	$190.68	13.580%	$216.5743	$216.57	$216.55	$216.60
Purchase #3	$92.96	5.738%	$98.294	$98.29	$98.30	$98.30
Purchase #4	$186.67	13.127%	$211.1742	$211.17	$211.15	$211.20
Purchase #5	$29.66	11.559%	$33.0884	$33.09	$33.10	$33.10
Purchase #6	$153.61	11.637%	$171.4856	$171.49	$171.50	$171.50
Purchase #7	$180.62	5.795%	$191.0869	$191.09	$191.10	$191.10
7 purchase totals =	$932.68		$1,026.9224	$1,026.92	$1,026.90	$1,027.00