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	$250.44	5.103%	$263.22	$263.22	$263.20	$263.20
Purchase #2	$197.32	11.765%	$220.5347	$220.53	$220.55	$220.50
Purchase #3	$112.75	11.532%	$125.7523	$125.75	$125.75	$125.80
Purchase #4	$163.85	13.453%	$185.8927	$185.89	$185.90	$185.90
Purchase #5	$106.91	4.502%	$111.7231	$111.72	$111.70	$111.70
Purchase #6	$195.89	5.837%	$207.3241	$207.32	$207.30	$207.30
Purchase #7	$114.74	11.425%	$127.849	$127.85	$127.85	$127.80
7 purchase totals =	$1,141.90		$1,242.2959	$1,242.28	$1,242.25	$1,242.20