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	$206.25	13.135%	$233.3409	$233.34	$233.35	$233.30
Purchase #2	$56.69	8.873%	$61.7201	$61.72	$61.70	$61.70
Purchase #3	$147.97	13.353%	$167.7284	$167.73	$167.75	$167.70
Purchase #4	$148.28	13.312%	$168.019	$168.02	$168.00	$168.00
Purchase #5	$220.91	3.431%	$228.4894	$228.49	$228.50	$228.50
Purchase #6	$54.92	11.623%	$61.3034	$61.30	$61.30	$61.30
Purchase #7	$210.72	4.810%	$220.8556	$220.86	$220.85	$220.90
7 purchase totals =	$1,045.74		$1,141.4568	$1,141.46	$1,141.45	$1,141.40