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	$51.47	7.167%	$55.1589	$55.16	$55.15	$55.20
Purchase #2	$64.66	12.463%	$72.7186	$72.72	$72.70	$72.70
Purchase #3	$244.26	10.351%	$269.5434	$269.54	$269.55	$269.50
Purchase #4	$59.88	7.639%	$64.4542	$64.45	$64.45	$64.50
Purchase #5	$50.29	11.627%	$56.1372	$56.14	$56.15	$56.10
Purchase #6	$105.91	3.723%	$109.853	$109.85	$109.85	$109.90
Purchase #7	$160.97	3.314%	$166.3045	$166.30	$166.30	$166.30
7 purchase totals =	$737.44		$794.1698	$794.16	$794.15	$794.20