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	$219.52	8.780%	$238.7939	$238.79	$238.80	$238.80
Purchase #2	$234.25	11.436%	$261.0388	$261.04	$261.05	$261.00
Purchase #3	$147.86	13.163%	$167.3228	$167.32	$167.30	$167.30
Purchase #4	$154.41	7.120%	$165.404	$165.40	$165.40	$165.40
Purchase #5	$139.88	3.598%	$144.9129	$144.91	$144.90	$144.90
Purchase #6	$236.92	8.603%	$257.3022	$257.30	$257.30	$257.30
Purchase #7	$176.31	11.473%	$196.538	$196.54	$196.55	$196.50
7 purchase totals =	$1,309.15		$1,431.3126	$1,431.30	$1,431.30	$1,431.20