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	$222.86	10.523%	$246.3116	$246.31	$246.30	$246.30
Purchase #2	$139.37	5.166%	$146.5699	$146.57	$146.55	$146.60
Purchase #3	$189.70	13.765%	$215.8122	$215.81	$215.80	$215.80
Purchase #4	$140.81	10.397%	$155.45	$155.45	$155.45	$155.50
Purchase #5	$182.29	3.312%	$188.3274	$188.33	$188.35	$188.30
Purchase #6	$43.54	4.118%	$45.333	$45.33	$45.35	$45.30
Purchase #7	$195.54	8.243%	$211.6584	$211.66	$211.65	$211.70
7 purchase totals =	$1,114.11		$1,209.4625	$1,209.46	$1,209.45	$1,209.50