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	$47.74	10.373%	$52.6921	$52.69	$52.70	$52.70
Purchase #2	$136.35	7.809%	$146.9976	$147.00	$147.00	$147.00
Purchase #3	$96.34	9.838%	$105.8179	$105.82	$105.80	$105.80
Purchase #4	$205.82	3.275%	$212.5606	$212.56	$212.55	$212.60
Purchase #5	$20.25	6.840%	$21.6351	$21.64	$21.65	$21.60
Purchase #6	$214.44	3.865%	$222.7281	$222.73	$222.75	$222.70
Purchase #7	$170.37	5.418%	$179.6006	$179.60	$179.60	$179.60
7 purchase totals =	$891.31		$942.0320	$942.04	$942.05	$942.00