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	$195.77	4.550%	$204.6775	$204.68	$204.70	$204.70
Purchase #2	$127.80	13.286%	$144.7795	$144.78	$144.80	$144.80
Purchase #3	$72.75	11.763%	$81.3076	$81.31	$81.30	$81.30
Purchase #4	$179.87	4.704%	$188.3311	$188.33	$188.35	$188.30
Purchase #5	$42.25	13.177%	$47.8173	$47.82	$47.80	$47.80
Purchase #6	$86.47	4.219%	$90.1182	$90.12	$90.10	$90.10
Purchase #7	$159.46	3.505%	$165.0491	$165.05	$165.05	$165.00
7 purchase totals =	$864.37		$922.0803	$922.09	$922.10	$922.00