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	$115.70	10.578%	$127.9387	$127.94	$127.95	$127.90
Purchase #2	$148.96	11.836%	$166.5909	$166.59	$166.60	$166.60
Purchase #3	$231.73	9.717%	$254.2472	$254.25	$254.25	$254.20
Purchase #4	$250.54	12.319%	$281.404	$281.40	$281.40	$281.40
Purchase #5	$12.87	9.228%	$14.0576	$14.06	$14.05	$14.10
Purchase #6	$200.46	4.561%	$209.603	$209.60	$209.60	$209.60
Purchase #7	$119.46	6.488%	$127.2106	$127.21	$127.20	$127.20
7 purchase totals =	$1,079.72		$1,181.0520	$1,181.05	$1,181.05	$1,181.00