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	$208.43	9.274%	$227.7598	$227.76	$227.75	$227.80
Purchase #2	$130.33	11.431%	$145.228	$145.23	$145.25	$145.20
Purchase #3	$43.96	3.751%	$45.6089	$45.61	$45.60	$45.60
Purchase #4	$147.32	13.159%	$166.7058	$166.71	$166.70	$166.70
Purchase #5	$69.26	4.307%	$72.243	$72.24	$72.25	$72.20
Purchase #6	$212.73	11.362%	$236.9004	$236.90	$236.90	$236.90
Purchase #7	$238.36	11.111%	$264.8442	$264.84	$264.85	$264.80
7 purchase totals =	$1,050.39		$1,159.2901	$1,159.29	$1,159.30	$1,159.20