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	$147.79	8.519%	$160.3802	$160.38	$160.40	$160.40
Purchase #2	$233.38	13.279%	$264.3705	$264.37	$264.35	$264.40
Purchase #3	$83.87	5.335%	$88.3445	$88.34	$88.35	$88.30
Purchase #4	$163.41	7.816%	$176.1821	$176.18	$176.20	$176.20
Purchase #5	$190.28	3.351%	$196.6563	$196.66	$196.65	$196.70
Purchase #6	$131.27	9.301%	$143.4794	$143.48	$143.50	$143.50
Purchase #7	$62.66	13.820%	$71.3196	$71.32	$71.30	$71.30
7 purchase totals =	$1,012.66		$1,100.7326	$1,100.73	$1,100.75	$1,100.80