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	$132.80	8.543%	$144.1451	$144.15	$144.15	$144.10
Purchase #2	$127.41	9.274%	$139.226	$139.23	$139.25	$139.20
Purchase #3	$142.72	6.428%	$151.894	$151.89	$151.90	$151.90
Purchase #4	$97.91	11.430%	$109.1011	$109.10	$109.10	$109.10
Purchase #5	$187.97	11.263%	$209.1411	$209.14	$209.15	$209.10
Purchase #6	$249.28	4.429%	$260.3206	$260.32	$260.30	$260.30
Purchase #7	$17.99	13.763%	$20.466	$20.47	$20.45	$20.50
7 purchase totals =	$956.08		$1,034.2939	$1,034.30	$1,034.30	$1,034.20