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	$93.61	10.772%	$103.6937	$103.69	$103.70	$103.70
Purchase #2	$58.37	8.228%	$63.1727	$63.17	$63.15	$63.20
Purchase #3	$179.33	9.578%	$196.5062	$196.51	$196.50	$196.50
Purchase #4	$28.42	12.152%	$31.8736	$31.87	$31.85	$31.90
Purchase #5	$154.28	7.234%	$165.4406	$165.44	$165.45	$165.40
Purchase #6	$80.39	5.326%	$84.6716	$84.67	$84.65	$84.70
Purchase #7	$94.56	4.839%	$99.1358	$99.14	$99.15	$99.10
7 purchase totals =	$688.96		$744.4942	$744.49	$744.45	$744.50