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	$118.42	4.482%	$123.7276	$123.73	$123.75	$123.70
Purchase #2	$127.59	10.500%	$140.987	$140.99	$141.00	$141.00
Purchase #3	$55.56	3.312%	$57.4001	$57.40	$57.40	$57.40
Purchase #4	$165.57	5.867%	$175.284	$175.28	$175.30	$175.30
Purchase #5	$43.35	7.361%	$46.541	$46.54	$46.55	$46.50
Purchase #6	$160.92	6.497%	$171.375	$171.38	$171.40	$171.40
Purchase #7	$69.60	5.144%	$73.1802	$73.18	$73.20	$73.20
7 purchase totals =	$741.01		$788.4949	$788.50	$788.60	$788.50