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	$199.70	10.448%	$220.5647	$220.56	$220.55	$220.60
Purchase #2	$51.70	9.792%	$56.7625	$56.76	$56.75	$56.80
Purchase #3	$118.35	6.673%	$126.2475	$126.25	$126.25	$126.20
Purchase #4	$165.40	9.665%	$181.3859	$181.39	$181.40	$181.40
Purchase #5	$91.88	5.457%	$96.8939	$96.89	$96.90	$96.90
Purchase #6	$56.67	8.801%	$61.6575	$61.66	$61.65	$61.70
Purchase #7	$40.72	11.852%	$45.5461	$45.55	$45.55	$45.50
7 purchase totals =	$724.42		$789.0581	$789.06	$789.05	$789.10