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	$47.73	5.550%	$50.379	$50.38	$50.40	$50.40
Purchase #2	$164.50	7.362%	$176.6105	$176.61	$176.60	$176.60
Purchase #3	$55.28	8.399%	$59.923	$59.92	$59.90	$59.90
Purchase #4	$108.37	5.118%	$113.9164	$113.92	$113.90	$113.90
Purchase #5	$235.51	4.488%	$246.0797	$246.08	$246.10	$246.10
Purchase #6	$157.47	4.463%	$164.4979	$164.50	$164.50	$164.50
Purchase #7	$173.97	8.471%	$188.707	$188.71	$188.70	$188.70
7 purchase totals =	$942.83		$1,000.1135	$1,000.12	$1,000.10	$1,000.10