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	$98.96	4.191%	$103.1074	$103.11	$103.10	$103.10
Purchase #2	$61.98	8.442%	$67.2124	$67.21	$67.20	$67.20
Purchase #3	$143.56	8.774%	$156.156	$156.16	$156.15	$156.20
Purchase #4	$172.27	10.552%	$190.4479	$190.45	$190.45	$190.40
Purchase #5	$242.25	3.506%	$250.7433	$250.74	$250.75	$250.70
Purchase #6	$150.40	4.611%	$157.3349	$157.33	$157.35	$157.30
Purchase #7	$126.95	9.634%	$139.1804	$139.18	$139.20	$139.20
7 purchase totals =	$996.37		$1,064.1823	$1,064.18	$1,064.20	$1,064.10