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	$162.43	13.456%	$184.2866	$184.29	$184.30	$184.30
Purchase #2	$99.89	9.420%	$109.2996	$109.30	$109.30	$109.30
Purchase #3	$230.25	6.436%	$245.0689	$245.07	$245.05	$245.10
Purchase #4	$79.35	9.299%	$86.7288	$86.73	$86.75	$86.70
Purchase #5	$131.70	8.304%	$142.6364	$142.64	$142.65	$142.60
Purchase #6	$92.39	13.407%	$104.7767	$104.78	$104.80	$104.80
Purchase #7	$166.62	11.375%	$185.573	$185.57	$185.55	$185.60
7 purchase totals =	$962.63		$1,058.3700	$1,058.38	$1,058.40	$1,058.40