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	$155.81	5.435%	$164.2783	$164.28	$164.30	$164.30
Purchase #2	$157.64	6.517%	$167.9134	$167.91	$167.90	$167.90
Purchase #3	$160.77	4.660%	$168.2619	$168.26	$168.25	$168.30
Purchase #4	$157.48	13.781%	$179.1823	$179.18	$179.20	$179.20
Purchase #5	$186.72	5.360%	$196.7282	$196.73	$196.75	$196.70
Purchase #6	$46.48	6.148%	$49.3376	$49.34	$49.35	$49.30
Purchase #7	$242.71	7.338%	$260.5201	$260.52	$260.50	$260.50
7 purchase totals =	$1,107.61		$1,186.2218	$1,186.22	$1,186.25	$1,186.20