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	$242.28	4.623%	$253.4806	$253.48	$253.50	$253.50
Purchase #2	$240.82	9.526%	$263.7605	$263.76	$263.75	$263.80
Purchase #3	$86.73	4.401%	$90.547	$90.55	$90.55	$90.50
Purchase #4	$98.60	13.360%	$111.773	$111.77	$111.75	$111.80
Purchase #5	$122.51	10.345%	$135.1837	$135.18	$135.20	$135.20
Purchase #6	$96.88	13.840%	$110.2882	$110.29	$110.30	$110.30
Purchase #7	$240.41	9.290%	$262.7441	$262.74	$262.75	$262.70
7 purchase totals =	$1,128.23		$1,227.7771	$1,227.77	$1,227.80	$1,227.80