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	$72.26	11.352%	$80.463	$80.46	$80.45	$80.50
Purchase #2	$187.25	5.765%	$198.045	$198.05	$198.05	$198.00
Purchase #3	$127.36	8.336%	$137.9767	$137.98	$138.00	$138.00
Purchase #4	$148.43	13.486%	$168.4473	$168.45	$168.45	$168.40
Purchase #5	$141.29	9.222%	$154.3198	$154.32	$154.30	$154.30
Purchase #6	$177.85	7.130%	$190.5307	$190.53	$190.55	$190.50
Purchase #7	$159.82	3.817%	$165.9203	$165.92	$165.90	$165.90
7 purchase totals =	$1,014.26		$1,095.7028	$1,095.71	$1,095.70	$1,095.60