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	$144.63	6.484%	$154.0078	$154.01	$154.00	$154.00
Purchase #2	$29.35	11.113%	$32.6117	$32.61	$32.60	$32.60
Purchase #3	$159.69	13.623%	$181.4446	$181.44	$181.45	$181.40
Purchase #4	$218.67	12.713%	$246.4695	$246.47	$246.45	$246.50
Purchase #5	$83.83	3.476%	$86.7439	$86.74	$86.75	$86.70
Purchase #6	$223.72	4.155%	$233.0156	$233.02	$233.00	$233.00
Purchase #7	$100.37	10.614%	$111.0233	$111.02	$111.00	$111.00
7 purchase totals =	$960.26		$1,045.3164	$1,045.31	$1,045.25	$1,045.20