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	$197.47	6.779%	$210.8565	$210.86	$210.85	$210.90
Purchase #2	$132.26	4.662%	$138.426	$138.43	$138.45	$138.40
Purchase #3	$231.31	13.117%	$261.6509	$261.65	$261.65	$261.70
Purchase #4	$96.69	12.867%	$109.1311	$109.13	$109.15	$109.10
Purchase #5	$56.37	4.757%	$59.0515	$59.05	$59.05	$59.10
Purchase #6	$140.36	13.581%	$159.4223	$159.42	$159.40	$159.40
Purchase #7	$162.83	5.560%	$171.8833	$171.88	$171.90	$171.90
7 purchase totals =	$1,017.29		$1,110.4216	$1,110.42	$1,110.45	$1,110.50