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	$69.63	10.272%	$76.7824	$76.78	$76.80	$76.80
Purchase #2	$90.93	10.278%	$100.2758	$100.28	$100.30	$100.30
Purchase #3	$68.74	3.526%	$71.1638	$71.16	$71.15	$71.20
Purchase #4	$197.27	12.612%	$222.1497	$222.15	$222.15	$222.10
Purchase #5	$174.54	13.669%	$198.3979	$198.40	$198.40	$198.40
Purchase #6	$27.85	9.741%	$30.5629	$30.56	$30.55	$30.60
Purchase #7	$76.56	5.734%	$80.95	$80.95	$80.95	$81.00
7 purchase totals =	$705.52		$780.2825	$780.28	$780.30	$780.40