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	$133.76	13.792%	$152.2082	$152.21	$152.20	$152.20
Purchase #2	$207.33	5.572%	$218.8824	$218.88	$218.90	$218.90
Purchase #3	$106.91	8.802%	$116.3202	$116.32	$116.30	$116.30
Purchase #4	$35.75	6.241%	$37.9812	$37.98	$38.00	$38.00
Purchase #5	$168.29	11.430%	$187.5255	$187.53	$187.55	$187.50
Purchase #6	$211.32	9.728%	$231.8772	$231.88	$231.90	$231.90
Purchase #7	$177.72	4.515%	$185.7441	$185.74	$185.75	$185.70
7 purchase totals =	$1,041.08		$1,130.5388	$1,130.54	$1,130.60	$1,130.50