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	$55.67	10.566%	$61.5521	$61.55	$61.55	$61.60
Purchase #2	$105.84	3.137%	$109.1602	$109.16	$109.15	$109.20
Purchase #3	$91.62	9.509%	$100.3321	$100.33	$100.35	$100.30
Purchase #4	$89.35	7.143%	$95.7323	$95.73	$95.75	$95.70
Purchase #5	$147.66	10.170%	$162.677	$162.68	$162.70	$162.70
Purchase #6	$128.82	12.637%	$145.099	$145.10	$145.10	$145.10
Purchase #7	$54.91	10.724%	$60.7985	$60.80	$60.80	$60.80
7 purchase totals =	$673.87		$735.3512	$735.35	$735.40	$735.40