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	$181.36	4.500%	$189.5212	$189.52	$189.50	$189.50
Purchase #2	$208.29	11.619%	$232.4912	$232.49	$232.50	$232.50
Purchase #3	$18.28	11.206%	$20.3285	$20.33	$20.35	$20.30
Purchase #4	$104.39	10.419%	$115.2664	$115.27	$115.25	$115.30
Purchase #5	$228.31	6.637%	$243.4629	$243.46	$243.45	$243.50
Purchase #6	$56.95	9.345%	$62.272	$62.27	$62.25	$62.30
Purchase #7	$208.94	6.578%	$222.6841	$222.68	$222.70	$222.70
7 purchase totals =	$1,006.52		$1,086.0263	$1,086.02	$1,086.00	$1,086.10