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	$67.34	7.319%	$72.2686	$72.27	$72.25	$72.30
Purchase #2	$220.30	12.723%	$248.3288	$248.33	$248.35	$248.30
Purchase #3	$74.66	3.722%	$77.4388	$77.44	$77.45	$77.40
Purchase #4	$137.25	6.606%	$146.3167	$146.32	$146.30	$146.30
Purchase #5	$130.92	10.812%	$145.0751	$145.08	$145.10	$145.10
Purchase #6	$232.41	7.661%	$250.2149	$250.21	$250.20	$250.20
Purchase #7	$207.90	7.217%	$222.9041	$222.90	$222.90	$222.90
7 purchase totals =	$1,070.78		$1,162.5470	$1,162.55	$1,162.55	$1,162.50