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	$63.56	6.664%	$67.7956	$67.80	$67.80	$67.80
Purchase #2	$110.73	4.481%	$115.6918	$115.69	$115.70	$115.70
Purchase #3	$9.33	6.174%	$9.906	$9.91	$9.90	$9.90
Purchase #4	$159.72	3.859%	$165.8836	$165.88	$165.90	$165.90
Purchase #5	$89.65	11.232%	$99.7195	$99.72	$99.70	$99.70
Purchase #6	$30.31	13.182%	$34.3055	$34.31	$34.30	$34.30
Purchase #7	$189.99	3.461%	$196.5656	$196.57	$196.55	$196.60
7 purchase totals =	$653.29		$689.8676	$689.88	$689.85	$689.90