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	$87.73	11.507%	$97.8251	$97.83	$97.85	$97.80
Purchase #2	$55.49	13.833%	$63.1659	$63.17	$63.15	$63.20
Purchase #3	$178.58	7.251%	$191.5288	$191.53	$191.55	$191.50
Purchase #4	$205.92	13.410%	$233.5339	$233.53	$233.55	$233.50
Purchase #5	$112.37	6.228%	$119.3684	$119.37	$119.35	$119.40
Purchase #6	$120.56	6.284%	$128.136	$128.14	$128.15	$128.10
Purchase #7	$96.86	13.296%	$109.7385	$109.74	$109.75	$109.70
7 purchase totals =	$857.51		$943.2966	$943.31	$943.35	$943.20