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	$68.58	4.280%	$71.5152	$71.52	$71.50	$71.50
Purchase #2	$229.40	3.823%	$238.17	$238.17	$238.15	$238.20
Purchase #3	$157.76	7.193%	$169.1077	$169.11	$169.10	$169.10
Purchase #4	$169.37	3.116%	$174.6476	$174.65	$174.65	$174.60
Purchase #5	$128.52	7.303%	$137.9058	$137.91	$137.90	$137.90
Purchase #6	$106.39	7.531%	$114.4022	$114.40	$114.40	$114.40
Purchase #7	$243.80	10.526%	$269.4624	$269.46	$269.45	$269.50
7 purchase totals =	$1,103.82		$1,175.2109	$1,175.22	$1,175.15	$1,175.20