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	$148.98	11.764%	$166.506	$166.51	$166.50	$166.50
Purchase #2	$238.37	6.749%	$254.4576	$254.46	$254.45	$254.50
Purchase #3	$103.89	10.818%	$115.1288	$115.13	$115.15	$115.10
Purchase #4	$136.75	5.232%	$143.9048	$143.90	$143.90	$143.90
Purchase #5	$181.28	9.845%	$199.127	$199.13	$199.15	$199.10
Purchase #6	$131.25	11.629%	$146.5131	$146.51	$146.50	$146.50
Purchase #7	$114.90	7.361%	$123.3578	$123.36	$123.35	$123.40
7 purchase totals =	$1,055.42		$1,148.9951	$1,149.00	$1,149.00	$1,149.00