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	$214.56	6.720%	$228.9784	$228.98	$229.00	$229.00
Purchase #2	$50.39	11.859%	$56.3658	$56.37	$56.35	$56.40
Purchase #3	$223.98	9.592%	$245.4642	$245.46	$245.45	$245.50
Purchase #4	$37.72	12.386%	$42.392	$42.39	$42.40	$42.40
Purchase #5	$245.90	9.300%	$268.7687	$268.77	$268.75	$268.80
Purchase #6	$156.64	10.372%	$172.8867	$172.89	$172.90	$172.90
Purchase #7	$123.78	3.430%	$128.0257	$128.03	$128.05	$128.00
7 purchase totals =	$1,052.97		$1,142.8815	$1,142.89	$1,142.90	$1,143.00