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	$211.70	8.587%	$229.8787	$229.88	$229.90	$229.90
Purchase #2	$89.93	7.251%	$96.4508	$96.45	$96.45	$96.50
Purchase #3	$136.97	10.376%	$151.182	$151.18	$151.20	$151.20
Purchase #4	$66.98	8.461%	$72.6472	$72.65	$72.65	$72.60
Purchase #5	$107.33	8.782%	$116.7557	$116.76	$116.75	$116.80
Purchase #6	$79.45	3.583%	$82.2967	$82.30	$82.30	$82.30
Purchase #7	$244.97	3.333%	$253.1349	$253.13	$253.15	$253.10
7 purchase totals =	$937.33		$1,002.3460	$1,002.35	$1,002.40	$1,002.40