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	$73.46	13.765%	$83.5718	$83.57	$83.55	$83.60
Purchase #2	$231.31	13.482%	$262.4952	$262.50	$262.50	$262.50
Purchase #3	$13.85	13.531%	$15.724	$15.72	$15.70	$15.70
Purchase #4	$54.98	6.183%	$58.3794	$58.38	$58.40	$58.40
Purchase #5	$172.76	3.250%	$178.3747	$178.37	$178.35	$178.40
Purchase #6	$216.42	11.872%	$242.1134	$242.11	$242.10	$242.10
Purchase #7	$53.90	10.518%	$59.5692	$59.57	$59.55	$59.60
7 purchase totals =	$816.68		$900.2277	$900.22	$900.15	$900.30