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	$98.56	6.495%	$104.9615	$104.96	$104.95	$105.00
Purchase #2	$93.97	6.825%	$100.3835	$100.38	$100.40	$100.40
Purchase #3	$108.79	13.764%	$123.7639	$123.76	$123.75	$123.80
Purchase #4	$48.77	13.234%	$55.2242	$55.22	$55.20	$55.20
Purchase #5	$92.32	8.131%	$99.8265	$99.83	$99.85	$99.80
Purchase #6	$191.32	12.375%	$214.9959	$215.00	$215.00	$215.00
Purchase #7	$220.36	3.577%	$228.2423	$228.24	$228.25	$228.20
7 purchase totals =	$854.09		$927.3978	$927.39	$927.40	$927.40