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	$157.81	4.811%	$165.4022	$165.40	$165.40	$165.40
Purchase #2	$114.29	11.543%	$127.4825	$127.48	$127.50	$127.50
Purchase #3	$49.76	5.355%	$52.4246	$52.42	$52.40	$52.40
Purchase #4	$210.93	6.264%	$224.1427	$224.14	$224.15	$224.10
Purchase #5	$172.74	8.432%	$187.3054	$187.31	$187.30	$187.30
Purchase #6	$39.58	8.135%	$42.7998	$42.80	$42.80	$42.80
Purchase #7	$240.49	9.667%	$263.7382	$263.74	$263.75	$263.70
7 purchase totals =	$985.60		$1,063.2954	$1,063.29	$1,063.30	$1,063.20