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	$105.96	6.471%	$112.8167	$112.82	$112.80	$112.80
Purchase #2	$55.70	4.326%	$58.1096	$58.11	$58.10	$58.10
Purchase #3	$111.90	6.599%	$119.2843	$119.28	$119.30	$119.30
Purchase #4	$209.27	10.130%	$230.4691	$230.47	$230.45	$230.50
Purchase #5	$224.39	11.188%	$249.4948	$249.49	$249.50	$249.50
Purchase #6	$100.58	3.505%	$104.1053	$104.11	$104.10	$104.10
Purchase #7	$85.84	4.303%	$89.5337	$89.53	$89.55	$89.50
7 purchase totals =	$893.64		$963.8135	$963.81	$963.80	$963.80