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	$49.76	8.120%	$53.8005	$53.80	$53.80	$53.80
Purchase #2	$93.55	10.607%	$103.4728	$103.47	$103.45	$103.50
Purchase #3	$154.73	13.299%	$175.3075	$175.31	$175.30	$175.30
Purchase #4	$238.93	10.713%	$264.5266	$264.53	$264.55	$264.50
Purchase #5	$98.72	4.501%	$103.1634	$103.16	$103.15	$103.20
Purchase #6	$104.63	7.643%	$112.6269	$112.63	$112.65	$112.60
Purchase #7	$200.80	11.436%	$223.7635	$223.76	$223.75	$223.80
7 purchase totals =	$941.12		$1,036.6612	$1,036.66	$1,036.65	$1,036.70