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	$128.42	9.154%	$140.1756	$140.18	$140.20	$140.20
Purchase #2	$145.39	4.586%	$152.0576	$152.06	$152.05	$152.10
Purchase #3	$166.90	8.773%	$181.5421	$181.54	$181.55	$181.50
Purchase #4	$18.74	3.736%	$19.4401	$19.44	$19.45	$19.40
Purchase #5	$20.31	4.291%	$21.1815	$21.18	$21.20	$21.20
Purchase #6	$161.28	3.663%	$167.1877	$167.19	$167.20	$167.20
Purchase #7	$64.86	12.122%	$72.7223	$72.72	$72.70	$72.70
7 purchase totals =	$705.90		$754.3069	$754.31	$754.35	$754.30