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	$33.97	9.245%	$37.1105	$37.11	$37.10	$37.10
Purchase #2	$117.52	10.103%	$129.393	$129.39	$129.40	$129.40
Purchase #3	$62.82	5.295%	$66.1463	$66.15	$66.15	$66.10
Purchase #4	$222.37	3.224%	$229.5392	$229.54	$229.55	$229.50
Purchase #5	$120.30	8.333%	$130.3246	$130.32	$130.30	$130.30
Purchase #6	$51.42	12.109%	$57.6464	$57.65	$57.65	$57.60
Purchase #7	$126.97	3.250%	$131.0965	$131.10	$131.10	$131.10
7 purchase totals =	$735.37		$781.2565	$781.26	$781.25	$781.10