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	$182.99	12.236%	$205.3807	$205.38	$205.40	$205.40
Purchase #2	$98.31	8.701%	$106.864	$106.86	$106.85	$106.90
Purchase #3	$106.51	4.325%	$111.1166	$111.12	$111.10	$111.10
Purchase #4	$74.73	10.488%	$82.5677	$82.57	$82.55	$82.60
Purchase #5	$67.89	6.444%	$72.2648	$72.26	$72.25	$72.30
Purchase #6	$115.50	12.363%	$129.7793	$129.78	$129.80	$129.80
Purchase #7	$103.35	11.705%	$115.4471	$115.45	$115.45	$115.40
7 purchase totals =	$749.28		$823.4202	$823.42	$823.40	$823.50