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	$106.30	6.272%	$112.9671	$112.97	$112.95	$113.00
Purchase #2	$84.80	13.546%	$96.287	$96.29	$96.30	$96.30
Purchase #3	$95.61	11.193%	$106.3116	$106.31	$106.30	$106.30
Purchase #4	$65.61	3.380%	$67.8276	$67.83	$67.85	$67.80
Purchase #5	$46.88	13.193%	$53.0649	$53.06	$53.05	$53.10
Purchase #6	$119.31	9.606%	$130.7709	$130.77	$130.75	$130.80
Purchase #7	$58.27	12.119%	$65.3317	$65.33	$65.35	$65.30
7 purchase totals =	$576.78		$632.5608	$632.56	$632.55	$632.60