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	$69.56	3.307%	$71.8603	$71.86	$71.85	$71.90
Purchase #2	$159.94	8.696%	$173.8484	$173.85	$173.85	$173.80
Purchase #3	$31.53	7.474%	$33.8866	$33.89	$33.90	$33.90
Purchase #4	$161.75	8.162%	$174.952	$174.95	$174.95	$175.00
Purchase #5	$28.91	10.207%	$31.8608	$31.86	$31.85	$31.90
Purchase #6	$96.92	6.722%	$103.435	$103.44	$103.45	$103.40
Purchase #7	$232.58	10.236%	$256.3869	$256.39	$256.40	$256.40
7 purchase totals =	$781.19		$846.2300	$846.24	$846.25	$846.30