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	$178.69	10.124%	$196.7806	$196.78	$196.80	$196.80
Purchase #2	$132.77	11.430%	$147.9456	$147.95	$147.95	$147.90
Purchase #3	$155.50	6.312%	$165.3152	$165.32	$165.30	$165.30
Purchase #4	$245.55	10.661%	$271.7281	$271.73	$271.75	$271.70
Purchase #5	$221.99	5.149%	$233.4203	$233.42	$233.40	$233.40
Purchase #6	$114.63	3.197%	$118.2947	$118.29	$118.30	$118.30
Purchase #7	$117.53	11.791%	$131.388	$131.39	$131.40	$131.40
7 purchase totals =	$1,166.66		$1,264.8725	$1,264.88	$1,264.90	$1,264.80