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	$69.64	12.873%	$78.6048	$78.60	$78.60	$78.60
Purchase #2	$89.80	9.586%	$98.4082	$98.41	$98.40	$98.40
Purchase #3	$133.64	9.774%	$146.702	$146.70	$146.70	$146.70
Purchase #4	$229.69	4.851%	$240.8323	$240.83	$240.85	$240.80
Purchase #5	$134.27	12.507%	$151.0631	$151.06	$151.05	$151.10
Purchase #6	$147.36	13.713%	$167.5675	$167.57	$167.55	$167.60
Purchase #7	$118.41	6.784%	$126.4429	$126.44	$126.45	$126.40
7 purchase totals =	$922.81		$1,009.6208	$1,009.61	$1,009.60	$1,009.60