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	$101.49	11.270%	$112.9279	$112.93	$112.95	$112.90
Purchase #2	$108.46	9.617%	$118.8906	$118.89	$118.90	$118.90
Purchase #3	$52.55	4.145%	$54.7282	$54.73	$54.75	$54.70
Purchase #4	$140.96	12.650%	$158.7914	$158.79	$158.80	$158.80
Purchase #5	$96.69	3.220%	$99.8034	$99.80	$99.80	$99.80
Purchase #6	$241.54	8.494%	$262.0564	$262.06	$262.05	$262.10
Purchase #7	$200.37	10.312%	$221.0322	$221.03	$221.05	$221.00
7 purchase totals =	$942.06		$1,028.2301	$1,028.23	$1,028.30	$1,028.20