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	$172.27	7.814%	$185.7312	$185.73	$185.75	$185.70
Purchase #2	$78.74	9.204%	$85.9872	$85.99	$86.00	$86.00
Purchase #3	$142.28	6.837%	$152.0077	$152.01	$152.00	$152.00
Purchase #4	$54.91	11.689%	$61.3284	$61.33	$61.35	$61.30
Purchase #5	$208.75	4.599%	$218.3504	$218.35	$218.35	$218.40
Purchase #6	$189.71	4.734%	$198.6909	$198.69	$198.70	$198.70
Purchase #7	$155.70	10.623%	$172.24	$172.24	$172.25	$172.20
7 purchase totals =	$1,002.36		$1,074.3358	$1,074.34	$1,074.40	$1,074.30