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	$198.57	6.417%	$211.3122	$211.31	$211.30	$211.30
Purchase #2	$19.77	13.743%	$22.487	$22.49	$22.50	$22.50
Purchase #3	$176.31	3.782%	$182.978	$182.98	$183.00	$183.00
Purchase #4	$41.71	8.126%	$45.0994	$45.10	$45.10	$45.10
Purchase #5	$37.26	3.133%	$38.4274	$38.43	$38.45	$38.40
Purchase #6	$144.41	4.501%	$150.9099	$150.91	$150.90	$150.90
Purchase #7	$249.48	9.404%	$272.9411	$272.94	$272.95	$272.90
7 purchase totals =	$867.51		$924.1550	$924.16	$924.20	$924.10