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	$33.93	6.471%	$36.1256	$36.13	$36.15	$36.10
Purchase #2	$64.91	12.296%	$72.8913	$72.89	$72.90	$72.90
Purchase #3	$147.89	11.498%	$164.8944	$164.89	$164.90	$164.90
Purchase #4	$79.86	10.776%	$88.4657	$88.47	$88.45	$88.50
Purchase #5	$58.74	6.271%	$62.4236	$62.42	$62.40	$62.40
Purchase #6	$221.30	9.792%	$242.9697	$242.97	$242.95	$243.00
Purchase #7	$182.29	12.253%	$204.626	$204.63	$204.65	$204.60
7 purchase totals =	$788.92		$872.3963	$872.40	$872.40	$872.40