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	$133.46	13.143%	$151.0006	$151.00	$151.00	$151.00
Purchase #2	$159.32	3.649%	$165.1336	$165.13	$165.15	$165.10
Purchase #3	$34.96	8.763%	$38.0235	$38.02	$38.00	$38.00
Purchase #4	$136.88	4.337%	$142.8165	$142.82	$142.80	$142.80
Purchase #5	$238.89	8.786%	$259.8789	$259.88	$259.90	$259.90
Purchase #6	$60.38	8.196%	$65.3287	$65.33	$65.35	$65.30
Purchase #7	$42.32	6.446%	$45.0479	$45.05	$45.05	$45.00
7 purchase totals =	$806.21		$867.2297	$867.23	$867.25	$867.10