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	$163.61	4.582%	$171.1066	$171.11	$171.10	$171.10
Purchase #2	$205.37	3.673%	$212.9132	$212.91	$212.90	$212.90
Purchase #3	$142.81	9.155%	$155.8843	$155.88	$155.90	$155.90
Purchase #4	$231.59	5.756%	$244.9203	$244.92	$244.90	$244.90
Purchase #5	$32.61	8.536%	$35.3936	$35.39	$35.40	$35.40
Purchase #6	$166.54	13.711%	$189.3743	$189.37	$189.35	$189.40
Purchase #7	$185.32	3.247%	$191.3373	$191.34	$191.35	$191.30
7 purchase totals =	$1,127.85		$1,200.9296	$1,200.92	$1,200.90	$1,200.90