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	$104.64	6.347%	$111.2815	$111.28	$111.30	$111.30
Purchase #2	$113.90	13.596%	$129.3858	$129.39	$129.40	$129.40
Purchase #3	$99.37	5.200%	$104.5372	$104.54	$104.55	$104.50
Purchase #4	$193.88	9.272%	$211.8566	$211.86	$211.85	$211.90
Purchase #5	$147.90	11.642%	$165.1185	$165.12	$165.10	$165.10
Purchase #6	$204.63	6.537%	$218.0067	$218.01	$218.00	$218.00
Purchase #7	$55.48	9.114%	$60.5364	$60.54	$60.55	$60.50
7 purchase totals =	$919.80		$1,000.7227	$1,000.74	$1,000.75	$1,000.70