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	$175.62	4.470%	$183.4702	$183.47	$183.45	$183.50
Purchase #2	$245.53	6.251%	$260.8781	$260.88	$260.90	$260.90
Purchase #3	$200.64	10.864%	$222.4375	$222.44	$222.45	$222.40
Purchase #4	$82.67	3.373%	$85.4585	$85.46	$85.45	$85.50
Purchase #5	$100.56	12.426%	$113.0556	$113.06	$113.05	$113.10
Purchase #6	$71.88	6.413%	$76.4897	$76.49	$76.50	$76.50
Purchase #7	$169.89	3.170%	$175.2755	$175.28	$175.30	$175.30
7 purchase totals =	$1,046.79		$1,117.0651	$1,117.08	$1,117.10	$1,117.20