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	$183.96	13.808%	$209.3612	$209.36	$209.35	$209.40
Purchase #2	$180.92	6.417%	$192.5296	$192.53	$192.55	$192.50
Purchase #3	$52.51	9.475%	$57.4853	$57.49	$57.50	$57.50
Purchase #4	$174.50	5.841%	$184.6925	$184.69	$184.70	$184.70
Purchase #5	$10.90	11.563%	$12.1604	$12.16	$12.15	$12.20
Purchase #6	$35.78	5.441%	$37.7268	$37.73	$37.75	$37.70
Purchase #7	$134.74	5.791%	$142.5428	$142.54	$142.55	$142.50
7 purchase totals =	$773.31		$836.4986	$836.50	$836.55	$836.50