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	$158.98	13.464%	$180.3851	$180.39	$180.40	$180.40
Purchase #2	$199.77	11.591%	$222.9253	$222.93	$222.95	$222.90
Purchase #3	$212.69	12.152%	$238.5361	$238.54	$238.55	$238.50
Purchase #4	$232.88	5.445%	$245.5603	$245.56	$245.55	$245.60
Purchase #5	$22.72	12.266%	$25.5068	$25.51	$25.50	$25.50
Purchase #6	$77.77	13.552%	$88.3094	$88.31	$88.30	$88.30
Purchase #7	$112.92	10.217%	$124.457	$124.46	$124.45	$124.50
7 purchase totals =	$1,017.73		$1,125.6800	$1,125.70	$1,125.70	$1,125.70