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	$210.50	10.815%	$233.2656	$233.27	$233.25	$233.30
Purchase #2	$62.96	6.200%	$66.8635	$66.86	$66.85	$66.90
Purchase #3	$85.69	4.581%	$89.6155	$89.62	$89.60	$89.60
Purchase #4	$64.56	9.516%	$70.7035	$70.70	$70.70	$70.70
Purchase #5	$155.30	4.448%	$162.2077	$162.21	$162.20	$162.20
Purchase #6	$96.31	13.735%	$109.5382	$109.54	$109.55	$109.50
Purchase #7	$77.87	11.647%	$86.9395	$86.94	$86.95	$86.90
7 purchase totals =	$753.19		$819.1335	$819.14	$819.10	$819.10