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	$91.51	6.466%	$97.427	$97.43	$97.45	$97.40
Purchase #2	$79.76	3.112%	$82.2421	$82.24	$82.25	$82.20
Purchase #3	$161.31	12.749%	$181.8754	$181.88	$181.90	$181.90
Purchase #4	$145.83	6.372%	$155.1223	$155.12	$155.10	$155.10
Purchase #5	$211.81	10.133%	$233.2727	$233.27	$233.25	$233.30
Purchase #6	$170.58	11.844%	$190.7835	$190.78	$190.80	$190.80
Purchase #7	$157.64	12.834%	$177.8715	$177.87	$177.85	$177.90
7 purchase totals =	$1,018.44		$1,118.5945	$1,118.59	$1,118.60	$1,118.60