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	$216.51	13.473%	$245.6804	$245.68	$245.70	$245.70
Purchase #2	$88.28	12.496%	$99.3115	$99.31	$99.30	$99.30
Purchase #3	$161.38	7.641%	$173.711	$173.71	$173.70	$173.70
Purchase #4	$211.61	10.848%	$234.5655	$234.57	$234.55	$234.60
Purchase #5	$79.65	6.782%	$85.0519	$85.05	$85.05	$85.10
Purchase #6	$144.80	13.626%	$164.5304	$164.53	$164.55	$164.50
Purchase #7	$86.45	3.412%	$89.3997	$89.40	$89.40	$89.40
7 purchase totals =	$988.68		$1,092.2504	$1,092.25	$1,092.25	$1,092.30