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	$220.43	4.106%	$229.4809	$229.48	$229.50	$229.50
Purchase #2	$242.73	11.459%	$270.5444	$270.54	$270.55	$270.50
Purchase #3	$170.82	8.440%	$185.2372	$185.24	$185.25	$185.20
Purchase #4	$196.43	4.241%	$204.7606	$204.76	$204.75	$204.80
Purchase #5	$27.72	3.146%	$28.5921	$28.59	$28.60	$28.60
Purchase #6	$62.28	11.418%	$69.3911	$69.39	$69.40	$69.40
Purchase #7	$35.78	4.724%	$37.4702	$37.47	$37.45	$37.50
7 purchase totals =	$956.19		$1,025.4765	$1,025.47	$1,025.50	$1,025.50