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	$238.82	8.506%	$259.134	$259.13	$259.15	$259.10
Purchase #2	$100.63	12.781%	$113.4915	$113.49	$113.50	$113.50
Purchase #3	$61.81	4.705%	$64.7182	$64.72	$64.70	$64.70
Purchase #4	$144.93	3.322%	$149.7446	$149.74	$149.75	$149.70
Purchase #5	$35.49	4.428%	$37.0615	$37.06	$37.05	$37.10
Purchase #6	$215.63	3.450%	$223.0692	$223.07	$223.05	$223.10
Purchase #7	$158.63	6.104%	$168.3128	$168.31	$168.30	$168.30
7 purchase totals =	$955.94		$1,015.5318	$1,015.52	$1,015.50	$1,015.50