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	$32.80	13.227%	$37.1385	$37.14	$37.15	$37.10
Purchase #2	$151.33	10.598%	$167.368	$167.37	$167.35	$167.40
Purchase #3	$96.94	10.803%	$107.4124	$107.41	$107.40	$107.40
Purchase #4	$32.64	7.761%	$35.1732	$35.17	$35.15	$35.20
Purchase #5	$9.99	9.478%	$10.9369	$10.94	$10.95	$10.90
Purchase #6	$117.88	11.362%	$131.2735	$131.27	$131.25	$131.30
Purchase #7	$92.73	6.151%	$98.4338	$98.43	$98.45	$98.40
7 purchase totals =	$534.31		$587.7363	$587.73	$587.70	$587.70