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	$156.49	9.360%	$171.1375	$171.14	$171.15	$171.10
Purchase #2	$46.46	10.311%	$51.2505	$51.25	$51.25	$51.30
Purchase #3	$78.54	12.234%	$88.1486	$88.15	$88.15	$88.10
Purchase #4	$41.46	3.830%	$43.0479	$43.05	$43.05	$43.00
Purchase #5	$135.79	11.860%	$151.8947	$151.89	$151.90	$151.90
Purchase #6	$109.42	6.641%	$116.6866	$116.69	$116.70	$116.70
Purchase #7	$99.31	9.233%	$108.4793	$108.48	$108.50	$108.50
7 purchase totals =	$667.47		$730.6451	$730.65	$730.70	$730.60