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	$134.64	13.590%	$152.9376	$152.94	$152.95	$152.90
Purchase #2	$58.72	5.191%	$61.7682	$61.77	$61.75	$61.80
Purchase #3	$107.58	4.254%	$112.1565	$112.16	$112.15	$112.20
Purchase #4	$171.63	8.677%	$186.5223	$186.52	$186.50	$186.50
Purchase #5	$234.70	4.607%	$245.5126	$245.51	$245.50	$245.50
Purchase #6	$59.57	5.114%	$62.6164	$62.62	$62.60	$62.60
Purchase #7	$211.46	8.654%	$229.7597	$229.76	$229.75	$229.80
7 purchase totals =	$978.30		$1,051.2733	$1,051.28	$1,051.20	$1,051.30