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	$230.36	5.511%	$243.0551	$243.06	$243.05	$243.10
Purchase #2	$236.91	11.610%	$264.4153	$264.42	$264.40	$264.40
Purchase #3	$161.79	3.150%	$166.8864	$166.89	$166.90	$166.90
Purchase #4	$32.59	10.215%	$35.9191	$35.92	$35.90	$35.90
Purchase #5	$133.88	13.806%	$152.3635	$152.36	$152.35	$152.40
Purchase #6	$104.78	7.617%	$112.7611	$112.76	$112.75	$112.80
Purchase #7	$68.30	13.488%	$77.5123	$77.51	$77.50	$77.50
7 purchase totals =	$968.61		$1,052.9128	$1,052.92	$1,052.85	$1,053.00