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	$85.39	11.141%	$94.9033	$94.90	$94.90	$94.90
Purchase #2	$79.54	3.490%	$82.3159	$82.32	$82.30	$82.30
Purchase #3	$100.81	5.128%	$105.9795	$105.98	$106.00	$106.00
Purchase #4	$154.41	12.632%	$173.9151	$173.92	$173.90	$173.90
Purchase #5	$235.28	7.168%	$252.1449	$252.14	$252.15	$252.10
Purchase #6	$160.95	6.316%	$171.1156	$171.12	$171.10	$171.10
Purchase #7	$170.26	6.816%	$181.8649	$181.86	$181.85	$181.90
7 purchase totals =	$986.64		$1,062.2392	$1,062.24	$1,062.20	$1,062.20