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	$166.99	4.634%	$174.7283	$174.73	$174.75	$174.70
Purchase #2	$152.35	13.858%	$173.4627	$173.46	$173.45	$173.50
Purchase #3	$18.88	6.664%	$20.1382	$20.14	$20.15	$20.10
Purchase #4	$127.32	6.280%	$135.3157	$135.32	$135.30	$135.30
Purchase #5	$81.59	9.835%	$89.6144	$89.61	$89.60	$89.60
Purchase #6	$249.98	7.710%	$269.2535	$269.25	$269.25	$269.30
Purchase #7	$101.99	6.864%	$108.9906	$108.99	$109.00	$109.00
7 purchase totals =	$899.10		$971.5034	$971.50	$971.50	$971.50