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	$53.78	3.802%	$55.8247	$55.82	$55.80	$55.80
Purchase #2	$189.44	3.534%	$196.1348	$196.13	$196.15	$196.10
Purchase #3	$88.72	6.456%	$94.4478	$94.45	$94.45	$94.40
Purchase #4	$168.70	6.676%	$179.9624	$179.96	$179.95	$180.00
Purchase #5	$80.28	13.173%	$90.8553	$90.86	$90.85	$90.90
Purchase #6	$197.44	5.502%	$208.3031	$208.30	$208.30	$208.30
Purchase #7	$170.37	6.434%	$181.3316	$181.33	$181.35	$181.30
7 purchase totals =	$948.73		$1,006.8597	$1,006.85	$1,006.85	$1,006.80