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	$197.26	12.615%	$222.1443	$222.14	$222.15	$222.10
Purchase #2	$201.56	9.284%	$220.2728	$220.27	$220.25	$220.30
Purchase #3	$48.29	12.424%	$54.2895	$54.29	$54.30	$54.30
Purchase #4	$148.44	12.854%	$167.5205	$167.52	$167.50	$167.50
Purchase #5	$147.98	3.332%	$152.9107	$152.91	$152.90	$152.90
Purchase #6	$209.35	13.821%	$238.2843	$238.28	$238.30	$238.30
Purchase #7	$31.72	7.578%	$34.1237	$34.12	$34.10	$34.10
7 purchase totals =	$984.60		$1,089.5458	$1,089.53	$1,089.50	$1,089.50