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	$110.88	11.350%	$123.4649	$123.46	$123.45	$123.50
Purchase #2	$91.77	3.136%	$94.6479	$94.65	$94.65	$94.60
Purchase #3	$62.62	10.222%	$69.021	$69.02	$69.00	$69.00
Purchase #4	$164.95	4.131%	$171.7641	$171.76	$171.75	$171.80
Purchase #5	$247.69	10.267%	$273.1203	$273.12	$273.10	$273.10
Purchase #6	$198.69	10.430%	$219.4134	$219.41	$219.40	$219.40
Purchase #7	$89.93	6.110%	$95.4247	$95.42	$95.40	$95.40
7 purchase totals =	$966.53		$1,046.8563	$1,046.84	$1,046.75	$1,046.80