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	$184.72	5.321%	$194.549	$194.55	$194.55	$194.50
Purchase #2	$47.96	12.221%	$53.8212	$53.82	$53.80	$53.80
Purchase #3	$130.41	13.169%	$147.5837	$147.58	$147.60	$147.60
Purchase #4	$17.28	13.543%	$19.6202	$19.62	$19.60	$19.60
Purchase #5	$119.78	6.483%	$127.5453	$127.55	$127.55	$127.50
Purchase #6	$189.92	10.769%	$210.3725	$210.37	$210.35	$210.40
Purchase #7	$50.29	5.305%	$52.9579	$52.96	$52.95	$53.00
7 purchase totals =	$740.36		$806.4498	$806.45	$806.40	$806.40