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	$48.49	11.722%	$54.174	$54.17	$54.15	$54.20
Purchase #2	$68.46	4.683%	$71.666	$71.67	$71.65	$71.70
Purchase #3	$158.72	4.653%	$166.1052	$166.11	$166.10	$166.10
Purchase #4	$102.25	7.360%	$109.7756	$109.78	$109.80	$109.80
Purchase #5	$142.73	3.385%	$147.5614	$147.56	$147.55	$147.60
Purchase #6	$96.73	13.566%	$109.8524	$109.85	$109.85	$109.90
Purchase #7	$91.99	5.328%	$96.8912	$96.89	$96.90	$96.90
7 purchase totals =	$709.37		$756.0258	$756.03	$756.00	$756.20