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	$205.40	3.639%	$212.8745	$212.87	$212.85	$212.90
Purchase #2	$166.76	3.815%	$173.1219	$173.12	$173.10	$173.10
Purchase #3	$55.47	4.391%	$57.9057	$57.91	$57.90	$57.90
Purchase #4	$116.28	13.145%	$131.565	$131.57	$131.55	$131.60
Purchase #5	$131.76	10.360%	$145.4103	$145.41	$145.40	$145.40
Purchase #6	$58.41	3.732%	$60.5899	$60.59	$60.60	$60.60
Purchase #7	$210.30	9.507%	$230.2932	$230.29	$230.30	$230.30
7 purchase totals =	$944.38		$1,011.7605	$1,011.76	$1,011.70	$1,011.80