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	$195.81	9.150%	$213.7266	$213.73	$213.75	$213.70
Purchase #2	$130.30	11.196%	$144.8884	$144.89	$144.90	$144.90
Purchase #3	$185.51	12.815%	$209.2831	$209.28	$209.30	$209.30
Purchase #4	$79.38	3.180%	$81.9043	$81.90	$81.90	$81.90
Purchase #5	$110.97	11.682%	$123.9335	$123.93	$123.95	$123.90
Purchase #6	$202.76	3.141%	$209.1287	$209.13	$209.15	$209.10
Purchase #7	$78.73	13.406%	$89.2845	$89.28	$89.30	$89.30
7 purchase totals =	$983.46		$1,072.1491	$1,072.14	$1,072.25	$1,072.10