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	$159.34	8.551%	$172.9652	$172.97	$172.95	$173.00
Purchase #2	$154.28	6.363%	$164.0968	$164.10	$164.10	$164.10
Purchase #3	$82.56	8.534%	$89.6057	$89.61	$89.60	$89.60
Purchase #4	$190.55	10.414%	$210.3939	$210.39	$210.40	$210.40
Purchase #5	$221.33	7.658%	$238.2795	$238.28	$238.30	$238.30
Purchase #6	$141.98	12.663%	$159.9589	$159.96	$159.95	$160.00
Purchase #7	$13.71	5.297%	$14.4362	$14.44	$14.45	$14.40
7 purchase totals =	$963.75		$1,049.7362	$1,049.75	$1,049.75	$1,049.80