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	$59.45	6.179%	$63.1234	$63.12	$63.10	$63.10
Purchase #2	$233.28	7.389%	$250.5171	$250.52	$250.50	$250.50
Purchase #3	$231.34	13.710%	$263.0567	$263.06	$263.05	$263.10
Purchase #4	$95.76	9.463%	$104.8218	$104.82	$104.80	$104.80
Purchase #5	$197.30	8.299%	$213.6739	$213.67	$213.65	$213.70
Purchase #6	$79.44	3.589%	$82.2911	$82.29	$82.30	$82.30
Purchase #7	$120.96	11.149%	$134.4458	$134.45	$134.45	$134.40
7 purchase totals =	$1,017.53		$1,111.9298	$1,111.93	$1,111.85	$1,111.90