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	$142.48	6.109%	$151.1841	$151.18	$151.20	$151.20
Purchase #2	$79.70	13.749%	$90.658	$90.66	$90.65	$90.70
Purchase #3	$49.52	10.437%	$54.6884	$54.69	$54.70	$54.70
Purchase #4	$103.55	12.597%	$116.5942	$116.59	$116.60	$116.60
Purchase #5	$188.87	5.163%	$198.6214	$198.62	$198.60	$198.60
Purchase #6	$206.42	7.301%	$221.4907	$221.49	$221.50	$221.50
Purchase #7	$165.97	12.459%	$186.6482	$186.65	$186.65	$186.60
7 purchase totals =	$936.51		$1,019.8850	$1,019.88	$1,019.90	$1,019.90