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	$238.62	6.149%	$253.2927	$253.29	$253.30	$253.30
Purchase #2	$190.83	5.792%	$201.8829	$201.88	$201.90	$201.90
Purchase #3	$220.44	8.117%	$238.3331	$238.33	$238.35	$238.30
Purchase #4	$133.25	11.204%	$148.1793	$148.18	$148.20	$148.20
Purchase #5	$72.46	11.412%	$80.7291	$80.73	$80.75	$80.70
Purchase #6	$98.92	6.848%	$105.694	$105.69	$105.70	$105.70
Purchase #7	$117.82	4.834%	$123.5154	$123.52	$123.50	$123.50
7 purchase totals =	$1,072.34		$1,151.6265	$1,151.62	$1,151.70	$1,151.60