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	$242.52	8.251%	$262.5303	$262.53	$262.55	$262.50
Purchase #2	$150.53	4.322%	$157.0359	$157.04	$157.05	$157.00
Purchase #3	$167.30	12.860%	$188.8148	$188.81	$188.80	$188.80
Purchase #4	$49.48	13.395%	$56.1078	$56.11	$56.10	$56.10
Purchase #5	$131.49	10.483%	$145.2741	$145.27	$145.25	$145.30
Purchase #6	$189.88	12.136%	$212.9238	$212.92	$212.90	$212.90
Purchase #7	$98.51	6.118%	$104.5368	$104.54	$104.55	$104.50
7 purchase totals =	$1,029.71		$1,127.2235	$1,127.22	$1,127.20	$1,127.10