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	$98.48	8.402%	$106.7543	$106.75	$106.75	$106.80
Purchase #2	$190.91	9.645%	$209.3233	$209.32	$209.30	$209.30
Purchase #3	$57.30	4.103%	$59.651	$59.65	$59.65	$59.70
Purchase #4	$120.62	5.380%	$127.1094	$127.11	$127.10	$127.10
Purchase #5	$108.25	9.765%	$118.8206	$118.82	$118.80	$118.80
Purchase #6	$234.38	3.444%	$242.452	$242.45	$242.45	$242.50
Purchase #7	$15.67	4.143%	$16.3192	$16.32	$16.30	$16.30
7 purchase totals =	$825.61		$880.4298	$880.42	$880.35	$880.50