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	$199.52	6.818%	$213.1233	$213.12	$213.10	$213.10
Purchase #2	$94.69	9.460%	$103.6477	$103.65	$103.65	$103.60
Purchase #3	$113.96	4.195%	$118.7406	$118.74	$118.75	$118.70
Purchase #4	$123.96	10.624%	$137.1295	$137.13	$137.15	$137.10
Purchase #5	$190.40	3.401%	$196.8755	$196.88	$196.90	$196.90
Purchase #6	$202.28	4.234%	$210.8445	$210.84	$210.85	$210.80
Purchase #7	$138.39	6.849%	$147.8683	$147.87	$147.85	$147.90
7 purchase totals =	$1,063.20		$1,128.2294	$1,128.23	$1,128.25	$1,128.10