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	$158.89	8.817%	$172.8993	$172.90	$172.90	$172.90
Purchase #2	$161.28	4.592%	$168.686	$168.69	$168.70	$168.70
Purchase #3	$89.31	9.235%	$97.5578	$97.56	$97.55	$97.60
Purchase #4	$101.36	7.744%	$109.2093	$109.21	$109.20	$109.20
Purchase #5	$127.46	3.418%	$131.8166	$131.82	$131.80	$131.80
Purchase #6	$76.51	10.161%	$84.2842	$84.28	$84.30	$84.30
Purchase #7	$66.46	11.267%	$73.948	$73.95	$73.95	$73.90
7 purchase totals =	$781.27		$838.4012	$838.41	$838.40	$838.40