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	$95.29	6.524%	$101.5067	$101.51	$101.50	$101.50
Purchase #2	$46.80	8.192%	$50.6339	$50.63	$50.65	$50.60
Purchase #3	$236.73	11.272%	$263.4142	$263.41	$263.40	$263.40
Purchase #4	$90.35	4.583%	$94.4907	$94.49	$94.50	$94.50
Purchase #5	$33.85	4.200%	$35.2717	$35.27	$35.25	$35.30
Purchase #6	$109.92	12.299%	$123.4391	$123.44	$123.45	$123.40
Purchase #7	$142.40	3.700%	$147.6688	$147.67	$147.65	$147.70
7 purchase totals =	$755.34		$816.4251	$816.42	$816.40	$816.40