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	$191.31	10.615%	$211.6176	$211.62	$211.60	$211.60
Purchase #2	$107.28	4.288%	$111.8802	$111.88	$111.90	$111.90
Purchase #3	$156.63	10.618%	$173.261	$173.26	$173.25	$173.30
Purchase #4	$61.65	8.168%	$66.6856	$66.69	$66.70	$66.70
Purchase #5	$102.42	3.425%	$105.9279	$105.93	$105.95	$105.90
Purchase #6	$70.65	11.236%	$78.5882	$78.59	$78.60	$78.60
Purchase #7	$239.98	12.557%	$270.1143	$270.11	$270.10	$270.10
7 purchase totals =	$929.92		$1,018.0748	$1,018.08	$1,018.10	$1,018.10