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	$59.25	9.225%	$64.7158	$64.72	$64.70	$64.70
Purchase #2	$80.76	11.269%	$89.8608	$89.86	$89.85	$89.90
Purchase #3	$203.80	3.861%	$211.6687	$211.67	$211.65	$211.70
Purchase #4	$33.84	7.417%	$36.3499	$36.35	$36.35	$36.30
Purchase #5	$240.68	11.809%	$269.1019	$269.10	$269.10	$269.10
Purchase #6	$223.60	4.694%	$234.0958	$234.10	$234.10	$234.10
Purchase #7	$154.76	11.706%	$172.8762	$172.88	$172.90	$172.90
7 purchase totals =	$996.69		$1,078.6691	$1,078.68	$1,078.65	$1,078.70