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	$134.69	7.861%	$145.278	$145.28	$145.30	$145.30
Purchase #2	$50.53	11.459%	$56.3202	$56.32	$56.30	$56.30
Purchase #3	$210.74	3.847%	$218.8472	$218.85	$218.85	$218.80
Purchase #4	$96.55	4.121%	$100.5288	$100.53	$100.55	$100.50
Purchase #5	$146.33	6.378%	$155.6629	$155.66	$155.65	$155.70
Purchase #6	$28.80	8.110%	$31.1357	$31.14	$31.15	$31.10
Purchase #7	$78.42	12.450%	$88.1833	$88.18	$88.20	$88.20
7 purchase totals =	$746.06		$795.9561	$795.96	$796.00	$795.90