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	$140.62	5.218%	$147.9576	$147.96	$147.95	$148.00
Purchase #2	$61.99	5.374%	$65.3213	$65.32	$65.30	$65.30
Purchase #3	$238.51	4.165%	$248.4439	$248.44	$248.45	$248.40
Purchase #4	$33.57	11.591%	$37.4611	$37.46	$37.45	$37.50
Purchase #5	$140.41	5.182%	$147.686	$147.69	$147.70	$147.70
Purchase #6	$164.91	5.800%	$174.4748	$174.47	$174.45	$174.50
Purchase #7	$232.78	10.262%	$256.6679	$256.67	$256.65	$256.70
7 purchase totals =	$1,012.79		$1,078.0126	$1,078.01	$1,077.95	$1,078.10