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	$156.88	9.477%	$171.7475	$171.75	$171.75	$171.70
Purchase #2	$85.81	10.499%	$94.8192	$94.82	$94.80	$94.80
Purchase #3	$55.51	6.514%	$59.1259	$59.13	$59.15	$59.10
Purchase #4	$44.98	9.549%	$49.2751	$49.28	$49.30	$49.30
Purchase #5	$180.38	10.294%	$198.9483	$198.95	$198.95	$198.90
Purchase #6	$211.56	10.504%	$233.7823	$233.78	$233.80	$233.80
Purchase #7	$203.67	4.447%	$212.7272	$212.73	$212.75	$212.70
7 purchase totals =	$938.79		$1,020.4255	$1,020.44	$1,020.50	$1,020.30