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	$167.82	7.769%	$180.8579	$180.86	$180.85	$180.90
Purchase #2	$10.30	9.384%	$11.2666	$11.27	$11.25	$11.30
Purchase #3	$113.46	13.317%	$128.5695	$128.57	$128.55	$128.60
Purchase #4	$79.93	9.766%	$87.736	$87.74	$87.75	$87.70
Purchase #5	$172.89	13.497%	$196.225	$196.23	$196.25	$196.20
Purchase #6	$108.42	6.113%	$115.0477	$115.05	$115.05	$115.00
Purchase #7	$168.73	3.645%	$174.8802	$174.88	$174.90	$174.90
7 purchase totals =	$821.55		$894.5829	$894.60	$894.60	$894.60