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	$223.90	8.704%	$243.3883	$243.39	$243.40	$243.40
Purchase #2	$53.77	9.846%	$59.0642	$59.06	$59.05	$59.10
Purchase #3	$130.44	13.820%	$148.4668	$148.47	$148.45	$148.50
Purchase #4	$247.99	8.624%	$269.3767	$269.38	$269.40	$269.40
Purchase #5	$30.52	10.861%	$33.8348	$33.83	$33.85	$33.80
Purchase #6	$130.70	9.170%	$142.6852	$142.69	$142.70	$142.70
Purchase #7	$210.39	11.399%	$234.3724	$234.37	$234.35	$234.40
7 purchase totals =	$1,027.71		$1,131.1884	$1,131.19	$1,131.20	$1,131.30