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	$101.51	7.428%	$109.0502	$109.05	$109.05	$109.10
Purchase #2	$211.67	7.817%	$228.2162	$228.22	$228.20	$228.20
Purchase #3	$115.35	10.616%	$127.5956	$127.60	$127.60	$127.60
Purchase #4	$187.61	13.723%	$213.3557	$213.36	$213.35	$213.40
Purchase #5	$118.64	3.871%	$123.2326	$123.23	$123.25	$123.20
Purchase #6	$249.26	6.336%	$265.0531	$265.05	$265.05	$265.10
Purchase #7	$40.97	3.643%	$42.4625	$42.46	$42.45	$42.50
7 purchase totals =	$1,025.01		$1,108.9659	$1,108.97	$1,108.95	$1,109.10