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	$147.40	10.412%	$162.7473	$162.75	$162.75	$162.70
Purchase #2	$235.75	13.391%	$267.3193	$267.32	$267.30	$267.30
Purchase #3	$70.30	12.140%	$78.8344	$78.83	$78.85	$78.80
Purchase #4	$69.81	11.593%	$77.9031	$77.90	$77.90	$77.90
Purchase #5	$105.96	10.433%	$117.0148	$117.01	$117.00	$117.00
Purchase #6	$120.52	12.729%	$135.861	$135.86	$135.85	$135.90
Purchase #7	$171.31	4.791%	$179.5175	$179.52	$179.50	$179.50
7 purchase totals =	$921.05		$1,019.1974	$1,019.19	$1,019.15	$1,019.10