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	$226.67	7.154%	$242.886	$242.89	$242.90	$242.90
Purchase #2	$217.40	8.746%	$236.4138	$236.41	$236.40	$236.40
Purchase #3	$111.88	12.483%	$125.846	$125.85	$125.85	$125.80
Purchase #4	$46.76	13.861%	$53.2414	$53.24	$53.25	$53.20
Purchase #5	$47.36	5.853%	$50.132	$50.13	$50.15	$50.10
Purchase #6	$112.69	6.312%	$119.803	$119.80	$119.80	$119.80
Purchase #7	$201.51	10.331%	$222.328	$222.33	$222.35	$222.30
7 purchase totals =	$964.27		$1,050.6502	$1,050.65	$1,050.70	$1,050.50