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	$54.46	12.523%	$61.28	$61.28	$61.30	$61.30
Purchase #2	$219.81	4.534%	$229.7762	$229.78	$229.80	$229.80
Purchase #3	$47.43	9.415%	$51.8955	$51.90	$51.90	$51.90
Purchase #4	$171.66	11.367%	$191.1726	$191.17	$191.15	$191.20
Purchase #5	$146.69	3.778%	$152.2319	$152.23	$152.25	$152.20
Purchase #6	$101.78	7.376%	$109.2873	$109.29	$109.30	$109.30
Purchase #7	$229.32	11.327%	$255.2951	$255.30	$255.30	$255.30
7 purchase totals =	$971.15		$1,050.9386	$1,050.95	$1,051.00	$1,051.00