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	$119.66	6.332%	$127.2369	$127.24	$127.25	$127.20
Purchase #2	$186.27	7.326%	$199.9161	$199.92	$199.90	$199.90
Purchase #3	$110.25	12.629%	$124.1735	$124.17	$124.15	$124.20
Purchase #4	$196.34	9.108%	$214.2226	$214.22	$214.20	$214.20
Purchase #5	$50.90	7.702%	$54.8203	$54.82	$54.80	$54.80
Purchase #6	$96.88	4.587%	$101.3239	$101.32	$101.30	$101.30
Purchase #7	$195.34	7.114%	$209.2365	$209.24	$209.25	$209.20
7 purchase totals =	$955.64		$1,030.9298	$1,030.93	$1,030.85	$1,030.80