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	$183.86	6.746%	$196.2632	$196.26	$196.25	$196.30
Purchase #2	$229.34	3.368%	$237.0642	$237.06	$237.05	$237.10
Purchase #3	$84.73	5.111%	$89.0606	$89.06	$89.05	$89.10
Purchase #4	$169.91	10.377%	$187.5416	$187.54	$187.55	$187.50
Purchase #5	$112.84	4.363%	$117.7632	$117.76	$117.75	$117.80
Purchase #6	$237.90	8.797%	$258.8281	$258.83	$258.85	$258.80
Purchase #7	$247.74	5.614%	$261.6481	$261.65	$261.65	$261.60
7 purchase totals =	$1,266.32		$1,348.1690	$1,348.16	$1,348.15	$1,348.20