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	$197.69	3.513%	$204.6348	$204.63	$204.65	$204.60
Purchase #2	$162.97	5.364%	$171.7117	$171.71	$171.70	$171.70
Purchase #3	$161.32	11.198%	$179.3846	$179.38	$179.40	$179.40
Purchase #4	$188.47	12.837%	$212.6639	$212.66	$212.65	$212.70
Purchase #5	$28.91	9.833%	$31.7527	$31.75	$31.75	$31.80
Purchase #6	$86.79	4.347%	$90.5628	$90.56	$90.55	$90.60
Purchase #7	$117.37	6.404%	$124.8864	$124.89	$124.90	$124.90
7 purchase totals =	$943.52		$1,015.5969	$1,015.58	$1,015.60	$1,015.70