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	$48.90	10.372%	$53.9719	$53.97	$53.95	$54.00
Purchase #2	$241.27	11.809%	$269.7616	$269.76	$269.75	$269.80
Purchase #3	$163.68	3.789%	$169.8818	$169.88	$169.90	$169.90
Purchase #4	$25.33	10.823%	$28.0715	$28.07	$28.05	$28.10
Purchase #5	$190.77	13.623%	$216.7586	$216.76	$216.75	$216.80
Purchase #6	$70.76	10.393%	$78.1141	$78.11	$78.10	$78.10
Purchase #7	$198.55	12.250%	$222.8724	$222.87	$222.85	$222.90
7 purchase totals =	$939.26		$1,039.4319	$1,039.42	$1,039.35	$1,039.60