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	$157.99	8.404%	$171.2675	$171.27	$171.25	$171.30
Purchase #2	$166.43	12.816%	$187.7597	$187.76	$187.75	$187.80
Purchase #3	$64.38	11.631%	$71.868	$71.87	$71.85	$71.90
Purchase #4	$90.85	6.674%	$96.9133	$96.91	$96.90	$96.90
Purchase #5	$223.69	9.443%	$244.813	$244.81	$244.80	$244.80
Purchase #6	$14.76	4.626%	$15.4428	$15.44	$15.45	$15.40
Purchase #7	$241.32	3.701%	$250.2513	$250.25	$250.25	$250.30
7 purchase totals =	$959.42		$1,038.3156	$1,038.31	$1,038.25	$1,038.40