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	$250.81	12.564%	$282.3218	$282.32	$282.30	$282.30
Purchase #2	$233.72	3.707%	$242.384	$242.38	$242.40	$242.40
Purchase #3	$25.80	12.381%	$28.9943	$28.99	$29.00	$29.00
Purchase #4	$125.42	3.580%	$129.91	$129.91	$129.90	$129.90
Purchase #5	$28.73	13.872%	$32.7154	$32.72	$32.70	$32.70
Purchase #6	$25.59	12.676%	$28.8338	$28.83	$28.85	$28.80
Purchase #7	$248.58	6.301%	$264.243	$264.24	$264.25	$264.20
7 purchase totals =	$938.65		$1,009.4023	$1,009.39	$1,009.40	$1,009.30