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	$150.38	9.440%	$164.5759	$164.58	$164.60	$164.60
Purchase #2	$39.95	8.435%	$43.3198	$43.32	$43.30	$43.30
Purchase #3	$104.48	13.777%	$118.8742	$118.87	$118.85	$118.90
Purchase #4	$53.56	11.288%	$59.6059	$59.61	$59.60	$59.60
Purchase #5	$183.56	10.206%	$202.2941	$202.29	$202.30	$202.30
Purchase #6	$87.53	4.585%	$91.5433	$91.54	$91.55	$91.50
Purchase #7	$247.41	4.589%	$258.7636	$258.76	$258.75	$258.80
7 purchase totals =	$866.87		$938.9768	$938.97	$938.95	$939.00