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	$191.46	3.564%	$198.2836	$198.28	$198.30	$198.30
Purchase #2	$237.83	7.495%	$255.6554	$255.66	$255.65	$255.70
Purchase #3	$47.80	10.618%	$52.8754	$52.88	$52.90	$52.90
Purchase #4	$233.95	11.738%	$261.4111	$261.41	$261.40	$261.40
Purchase #5	$100.70	4.513%	$105.2446	$105.24	$105.25	$105.20
Purchase #6	$104.34	5.324%	$109.8951	$109.90	$109.90	$109.90
Purchase #7	$127.64	4.130%	$132.9115	$132.91	$132.90	$132.90
7 purchase totals =	$1,043.72		$1,116.2767	$1,116.28	$1,116.30	$1,116.30