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	$130.50	4.216%	$136.0019	$136.00	$136.00	$136.00
Purchase #2	$79.38	4.268%	$82.7679	$82.77	$82.75	$82.80
Purchase #3	$244.75	11.254%	$272.2942	$272.29	$272.30	$272.30
Purchase #4	$72.79	6.812%	$77.7485	$77.75	$77.75	$77.70
Purchase #5	$18.64	13.444%	$21.146	$21.15	$21.15	$21.10
Purchase #6	$164.85	11.546%	$183.8836	$183.88	$183.90	$183.90
Purchase #7	$143.42	5.604%	$151.4573	$151.46	$151.45	$151.50
7 purchase totals =	$854.33		$925.2994	$925.30	$925.30	$925.30