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	$80.52	6.230%	$85.5364	$85.54	$85.55	$85.50
Purchase #2	$59.52	4.631%	$62.2764	$62.28	$62.30	$62.30
Purchase #3	$225.52	11.842%	$252.2261	$252.23	$252.25	$252.20
Purchase #4	$209.36	11.646%	$233.7421	$233.74	$233.75	$233.70
Purchase #5	$214.83	6.726%	$229.2795	$229.28	$229.30	$229.30
Purchase #6	$59.37	5.346%	$62.5439	$62.54	$62.55	$62.50
Purchase #7	$200.84	9.712%	$220.3456	$220.35	$220.35	$220.30
7 purchase totals =	$1,049.96		$1,145.9500	$1,145.96	$1,146.05	$1,145.80