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	$41.65	4.604%	$43.5676	$43.57	$43.55	$43.60
Purchase #2	$130.35	13.526%	$147.9811	$147.98	$148.00	$148.00
Purchase #3	$85.55	13.226%	$96.8648	$96.86	$96.85	$96.90
Purchase #4	$190.76	3.355%	$197.16	$197.16	$197.15	$197.20
Purchase #5	$57.93	6.301%	$61.5802	$61.58	$61.60	$61.60
Purchase #6	$18.55	12.696%	$20.9051	$20.91	$20.90	$20.90
Purchase #7	$102.48	4.679%	$107.275	$107.28	$107.30	$107.30
7 purchase totals =	$627.27		$675.3338	$675.34	$675.35	$675.50