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	$113.44	5.462%	$119.6361	$119.64	$119.65	$119.60
Purchase #2	$72.78	9.738%	$79.8673	$79.87	$79.85	$79.90
Purchase #3	$201.81	4.216%	$210.3183	$210.32	$210.30	$210.30
Purchase #4	$82.51	8.367%	$89.4136	$89.41	$89.40	$89.40
Purchase #5	$229.38	9.377%	$250.889	$250.89	$250.90	$250.90
Purchase #6	$173.56	8.623%	$188.5261	$188.53	$188.55	$188.50
Purchase #7	$38.80	7.287%	$41.6274	$41.63	$41.65	$41.60
7 purchase totals =	$912.28		$980.2778	$980.29	$980.30	$980.20