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	$123.47	5.559%	$130.3337	$130.33	$130.35	$130.30
Purchase #2	$202.70	9.787%	$222.5382	$222.54	$222.55	$222.50
Purchase #3	$191.60	12.383%	$215.3258	$215.33	$215.35	$215.30
Purchase #4	$165.86	7.523%	$178.3376	$178.34	$178.35	$178.30
Purchase #5	$90.69	7.276%	$97.2886	$97.29	$97.30	$97.30
Purchase #6	$91.44	9.776%	$100.3792	$100.38	$100.40	$100.40
Purchase #7	$92.86	11.155%	$103.2185	$103.22	$103.20	$103.20
7 purchase totals =	$958.62		$1,047.4216	$1,047.43	$1,047.50	$1,047.30