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	$34.50	11.342%	$38.413	$38.41	$38.40	$38.40
Purchase #2	$227.43	4.104%	$236.7637	$236.76	$236.75	$236.80
Purchase #3	$120.44	4.192%	$125.4888	$125.49	$125.50	$125.50
Purchase #4	$59.71	4.240%	$62.2417	$62.24	$62.25	$62.20
Purchase #5	$250.85	7.815%	$270.4539	$270.45	$270.45	$270.50
Purchase #6	$59.28	10.134%	$65.2874	$65.29	$65.30	$65.30
Purchase #7	$214.46	4.317%	$223.7182	$223.72	$223.70	$223.70
7 purchase totals =	$966.67		$1,022.3667	$1,022.36	$1,022.35	$1,022.40