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	$53.28	8.579%	$57.8509	$57.85	$57.85	$57.90
Purchase #2	$173.74	4.840%	$182.149	$182.15	$182.15	$182.10
Purchase #3	$196.62	13.818%	$223.789	$223.79	$223.80	$223.80
Purchase #4	$154.27	10.480%	$170.4375	$170.44	$170.45	$170.40
Purchase #5	$165.90	11.172%	$184.4343	$184.43	$184.45	$184.40
Purchase #6	$162.76	3.737%	$168.8423	$168.84	$168.85	$168.80
Purchase #7	$118.73	10.303%	$130.9628	$130.96	$130.95	$131.00
7 purchase totals =	$1,025.30		$1,118.4658	$1,118.46	$1,118.50	$1,118.40