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	$133.96	10.352%	$147.8275	$147.83	$147.85	$147.80
Purchase #2	$83.51	5.629%	$88.2108	$88.21	$88.20	$88.20
Purchase #3	$29.84	10.181%	$32.878	$32.88	$32.90	$32.90
Purchase #4	$154.64	11.590%	$172.5628	$172.56	$172.55	$172.60
Purchase #5	$53.87	10.223%	$59.3771	$59.38	$59.40	$59.40
Purchase #6	$127.35	13.333%	$144.3296	$144.33	$144.35	$144.30
Purchase #7	$218.30	12.368%	$245.2993	$245.30	$245.30	$245.30
7 purchase totals =	$801.47		$890.4851	$890.49	$890.55	$890.50