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	$94.73	11.182%	$105.3227	$105.32	$105.30	$105.30
Purchase #2	$117.78	9.670%	$129.1693	$129.17	$129.15	$129.20
Purchase #3	$240.42	6.652%	$256.4127	$256.41	$256.40	$256.40
Purchase #4	$164.78	12.473%	$185.333	$185.33	$185.35	$185.30
Purchase #5	$76.61	3.135%	$79.0117	$79.01	$79.00	$79.00
Purchase #6	$57.90	5.194%	$60.9073	$60.91	$60.90	$60.90
Purchase #7	$131.62	3.627%	$136.3939	$136.39	$136.40	$136.40
7 purchase totals =	$883.84		$952.5506	$952.54	$952.50	$952.50