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	$109.96	3.109%	$113.3787	$113.38	$113.40	$113.40
Purchase #2	$195.87	4.666%	$205.0093	$205.01	$205.00	$205.00
Purchase #3	$173.50	4.114%	$180.6378	$180.64	$180.65	$180.60
Purchase #4	$91.33	3.819%	$94.8179	$94.82	$94.80	$94.80
Purchase #5	$177.84	12.590%	$200.2301	$200.23	$200.25	$200.20
Purchase #6	$219.95	12.675%	$247.8287	$247.83	$247.85	$247.80
Purchase #7	$99.45	3.780%	$103.2092	$103.21	$103.20	$103.20
7 purchase totals =	$1,067.90		$1,145.1117	$1,145.12	$1,145.15	$1,145.00