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	$171.34	11.569%	$191.1623	$191.16	$191.15	$191.20
Purchase #2	$32.29	9.497%	$35.3566	$35.36	$35.35	$35.40
Purchase #3	$95.33	3.521%	$98.6866	$98.69	$98.70	$98.70
Purchase #4	$64.92	8.598%	$70.5018	$70.50	$70.50	$70.50
Purchase #5	$99.27	6.385%	$105.6084	$105.61	$105.60	$105.60
Purchase #6	$176.94	5.818%	$187.2344	$187.23	$187.25	$187.20
Purchase #7	$135.95	8.784%	$147.8918	$147.89	$147.90	$147.90
7 purchase totals =	$776.04		$836.4419	$836.44	$836.45	$836.50