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	$223.98	9.490%	$245.2357	$245.24	$245.25	$245.20
Purchase #2	$5.82	11.772%	$6.5051	$6.51	$6.50	$6.50
Purchase #3	$230.95	6.192%	$245.2504	$245.25	$245.25	$245.30
Purchase #4	$175.93	4.114%	$183.1678	$183.17	$183.15	$183.20
Purchase #5	$82.25	7.173%	$88.1498	$88.15	$88.15	$88.10
Purchase #6	$166.78	7.853%	$179.8772	$179.88	$179.90	$179.90
Purchase #7	$68.59	5.640%	$72.4585	$72.46	$72.45	$72.50
7 purchase totals =	$954.30		$1,020.6445	$1,020.66	$1,020.65	$1,020.70