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	$80.52	10.719%	$89.1509	$89.15	$89.15	$89.20
Purchase #2	$242.27	13.686%	$275.4271	$275.43	$275.45	$275.40
Purchase #3	$110.89	3.419%	$114.6813	$114.68	$114.70	$114.70
Purchase #4	$88.50	3.675%	$91.7524	$91.75	$91.75	$91.80
Purchase #5	$42.32	13.253%	$47.9287	$47.93	$47.95	$47.90
Purchase #6	$218.27	10.809%	$241.8628	$241.86	$241.85	$241.90
Purchase #7	$163.44	13.146%	$184.9258	$184.93	$184.95	$184.90
7 purchase totals =	$946.21		$1,045.7290	$1,045.73	$1,045.80	$1,045.80