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	$200.72	13.685%	$228.1885	$228.19	$228.20	$228.20
Purchase #2	$243.62	13.392%	$276.2456	$276.25	$276.25	$276.20
Purchase #3	$59.40	13.814%	$67.6055	$67.61	$67.60	$67.60
Purchase #4	$26.60	8.462%	$28.8509	$28.85	$28.85	$28.90
Purchase #5	$82.76	3.400%	$85.5738	$85.57	$85.55	$85.60
Purchase #6	$178.85	13.117%	$202.3098	$202.31	$202.30	$202.30
Purchase #7	$115.95	9.600%	$127.0812	$127.08	$127.10	$127.10
7 purchase totals =	$907.90		$1,015.8553	$1,015.86	$1,015.85	$1,015.90