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	$111.97	13.265%	$126.8228	$126.82	$126.80	$126.80
Purchase #2	$73.37	4.290%	$76.5176	$76.52	$76.50	$76.50
Purchase #3	$150.56	6.465%	$160.2937	$160.29	$160.30	$160.30
Purchase #4	$96.39	13.159%	$109.074	$109.07	$109.05	$109.10
Purchase #5	$139.66	5.632%	$147.5257	$147.53	$147.55	$147.50
Purchase #6	$141.72	5.581%	$149.6294	$149.63	$149.65	$149.60
Purchase #7	$24.81	10.703%	$27.4654	$27.47	$27.45	$27.50
7 purchase totals =	$738.48		$797.3286	$797.33	$797.30	$797.30