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	$94.77	11.185%	$105.37	$105.37	$105.35	$105.40
Purchase #2	$237.38	13.560%	$269.5687	$269.57	$269.55	$269.60
Purchase #3	$172.55	5.358%	$181.7952	$181.80	$181.80	$181.80
Purchase #4	$59.56	4.690%	$62.3534	$62.35	$62.35	$62.40
Purchase #5	$91.66	6.821%	$97.9121	$97.91	$97.90	$97.90
Purchase #6	$109.51	4.768%	$114.7314	$114.73	$114.75	$114.70
Purchase #7	$190.81	10.337%	$210.534	$210.53	$210.55	$210.50
7 purchase totals =	$956.24		$1,042.2648	$1,042.26	$1,042.25	$1,042.30