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	$148.53	4.736%	$155.5644	$155.56	$155.55	$155.60
Purchase #2	$34.26	9.572%	$37.5394	$37.54	$37.55	$37.50
Purchase #3	$96.27	13.377%	$109.148	$109.15	$109.15	$109.10
Purchase #4	$213.91	11.343%	$238.1738	$238.17	$238.15	$238.20
Purchase #5	$231.98	6.341%	$246.6899	$246.69	$246.70	$246.70
Purchase #6	$232.27	9.524%	$254.3914	$254.39	$254.40	$254.40
Purchase #7	$219.88	10.761%	$243.5413	$243.54	$243.55	$243.50
7 purchase totals =	$1,177.10		$1,285.0482	$1,285.04	$1,285.05	$1,285.00