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	$43.52	5.245%	$45.8026	$45.80	$45.80	$45.80
Purchase #2	$160.96	4.824%	$168.7247	$168.72	$168.70	$168.70
Purchase #3	$194.57	5.503%	$205.2772	$205.28	$205.30	$205.30
Purchase #4	$121.36	6.521%	$129.2739	$129.27	$129.25	$129.30
Purchase #5	$155.91	7.386%	$167.4255	$167.43	$167.45	$167.40
Purchase #6	$236.48	6.272%	$251.312	$251.31	$251.30	$251.30
Purchase #7	$33.56	5.629%	$35.4491	$35.45	$35.45	$35.40
7 purchase totals =	$946.36		$1,003.2650	$1,003.26	$1,003.25	$1,003.20