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	$168.73	5.857%	$178.6125	$178.61	$178.60	$178.60
Purchase #2	$171.33	13.248%	$194.0278	$194.03	$194.05	$194.00
Purchase #3	$49.37	12.613%	$55.597	$55.60	$55.60	$55.60
Purchase #4	$197.77	12.442%	$222.3765	$222.38	$222.40	$222.40
Purchase #5	$196.89	8.634%	$213.8895	$213.89	$213.90	$213.90
Purchase #6	$79.69	7.241%	$85.4604	$85.46	$85.45	$85.50
Purchase #7	$243.33	7.391%	$261.3145	$261.31	$261.30	$261.30
7 purchase totals =	$1,107.11		$1,211.2782	$1,211.28	$1,211.30	$1,211.30