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	$110.71	3.716%	$114.824	$114.82	$114.80	$114.80
Purchase #2	$198.35	12.718%	$223.5762	$223.58	$223.60	$223.60
Purchase #3	$55.48	10.709%	$61.4214	$61.42	$61.40	$61.40
Purchase #4	$64.37	13.464%	$73.0368	$73.04	$73.05	$73.00
Purchase #5	$107.61	13.465%	$122.0997	$122.10	$122.10	$122.10
Purchase #6	$99.98	9.272%	$109.2501	$109.25	$109.25	$109.30
Purchase #7	$189.83	10.695%	$210.1323	$210.13	$210.15	$210.10
7 purchase totals =	$826.33		$914.3405	$914.34	$914.35	$914.30