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	$188.47	4.163%	$196.316	$196.32	$196.30	$196.30
Purchase #2	$22.74	12.411%	$25.5623	$25.56	$25.55	$25.60
Purchase #3	$54.59	4.179%	$56.8713	$56.87	$56.85	$56.90
Purchase #4	$79.55	9.571%	$87.1637	$87.16	$87.15	$87.20
Purchase #5	$59.71	11.227%	$66.4136	$66.41	$66.40	$66.40
Purchase #6	$129.69	6.708%	$138.3896	$138.39	$138.40	$138.40
Purchase #7	$80.40	6.407%	$85.5512	$85.55	$85.55	$85.60
7 purchase totals =	$615.15		$656.2677	$656.26	$656.20	$656.40