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	$85.55	9.454%	$93.6379	$93.64	$93.65	$93.60
Purchase #2	$51.45	9.694%	$56.4376	$56.44	$56.45	$56.40
Purchase #3	$168.46	6.606%	$179.5885	$179.59	$179.60	$179.60
Purchase #4	$54.90	7.728%	$59.1427	$59.14	$59.15	$59.10
Purchase #5	$232.49	6.764%	$248.2156	$248.22	$248.20	$248.20
Purchase #6	$51.54	7.130%	$55.2148	$55.21	$55.20	$55.20
Purchase #7	$45.49	13.538%	$51.6484	$51.65	$51.65	$51.60
7 purchase totals =	$689.88		$743.8855	$743.89	$743.90	$743.70