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	$209.26	5.515%	$220.8007	$220.80	$220.80	$220.80
Purchase #2	$20.34	5.319%	$21.4219	$21.42	$21.40	$21.40
Purchase #3	$19.95	6.194%	$21.1857	$21.19	$21.20	$21.20
Purchase #4	$198.61	12.367%	$223.1721	$223.17	$223.15	$223.20
Purchase #5	$136.47	11.540%	$152.2186	$152.22	$152.20	$152.20
Purchase #6	$105.30	4.356%	$109.8869	$109.89	$109.90	$109.90
Purchase #7	$60.77	11.624%	$67.8339	$67.83	$67.85	$67.80
7 purchase totals =	$750.70		$816.5198	$816.52	$816.50	$816.50