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	$136.54	3.500%	$141.3189	$141.32	$141.30	$141.30
Purchase #2	$121.32	5.146%	$127.5631	$127.56	$127.55	$127.60
Purchase #3	$110.71	3.173%	$114.2228	$114.22	$114.20	$114.20
Purchase #4	$147.86	3.360%	$152.8281	$152.83	$152.85	$152.80
Purchase #5	$185.61	5.200%	$195.2617	$195.26	$195.25	$195.30
Purchase #6	$244.37	7.611%	$262.969	$262.97	$262.95	$263.00
Purchase #7	$139.25	6.364%	$148.1119	$148.11	$148.10	$148.10
7 purchase totals =	$1,085.66		$1,142.2755	$1,142.27	$1,142.20	$1,142.30