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	$46.25	7.219%	$49.5888	$49.59	$49.60	$49.60
Purchase #2	$55.41	11.507%	$61.786	$61.79	$61.80	$61.80
Purchase #3	$39.52	9.744%	$43.3708	$43.37	$43.35	$43.40
Purchase #4	$63.28	4.127%	$65.8916	$65.89	$65.90	$65.90
Purchase #5	$185.92	6.599%	$198.1889	$198.19	$198.20	$198.20
Purchase #6	$192.61	6.496%	$205.1219	$205.12	$205.10	$205.10
Purchase #7	$112.76	13.485%	$127.9657	$127.97	$127.95	$128.00
7 purchase totals =	$695.75		$751.9137	$751.92	$751.90	$752.00