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	$139.72	8.805%	$152.0223	$152.02	$152.00	$152.00
Purchase #2	$211.29	7.440%	$227.01	$227.01	$227.00	$227.00
Purchase #3	$235.50	11.846%	$263.3973	$263.40	$263.40	$263.40
Purchase #4	$232.33	5.592%	$245.3219	$245.32	$245.30	$245.30
Purchase #5	$87.78	11.541%	$97.9107	$97.91	$97.90	$97.90
Purchase #6	$57.50	13.761%	$65.4126	$65.41	$65.40	$65.40
Purchase #7	$224.39	8.525%	$243.5192	$243.52	$243.50	$243.50
7 purchase totals =	$1,188.51		$1,294.5940	$1,294.59	$1,294.50	$1,294.50