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	$38.38	8.620%	$41.6884	$41.69	$41.70	$41.70
Purchase #2	$6.65	10.581%	$7.3536	$7.35	$7.35	$7.40
Purchase #3	$30.94	9.108%	$33.758	$33.76	$33.75	$33.80
Purchase #4	$54.57	3.207%	$56.3201	$56.32	$56.30	$56.30
Purchase #5	$98.53	10.521%	$108.8963	$108.90	$108.90	$108.90
Purchase #6	$32.64	8.240%	$35.3295	$35.33	$35.35	$35.30
Purchase #7	$136.71	5.742%	$144.5599	$144.56	$144.55	$144.60
7 purchase totals =	$398.42		$427.9058	$427.91	$427.90	$428.00