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	$81.54	7.817%	$87.914	$87.91	$87.90	$87.90
Purchase #2	$194.92	10.443%	$215.2755	$215.28	$215.30	$215.30
Purchase #3	$138.28	8.654%	$150.2468	$150.25	$150.25	$150.20
Purchase #4	$51.80	10.753%	$57.3701	$57.37	$57.35	$57.40
Purchase #5	$54.30	13.598%	$61.6837	$61.68	$61.70	$61.70
Purchase #6	$186.37	13.452%	$211.4405	$211.44	$211.45	$211.40
Purchase #7	$231.56	11.111%	$257.2886	$257.29	$257.30	$257.30
7 purchase totals =	$938.77		$1,041.2192	$1,041.22	$1,041.25	$1,041.20