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	$244.38	4.244%	$254.7515	$254.75	$254.75	$254.80
Purchase #2	$98.28	11.540%	$109.6215	$109.62	$109.60	$109.60
Purchase #3	$162.40	4.317%	$169.4108	$169.41	$169.40	$169.40
Purchase #4	$27.52	10.323%	$30.3609	$30.36	$30.35	$30.40
Purchase #5	$94.71	4.855%	$99.3082	$99.31	$99.30	$99.30
Purchase #6	$91.50	9.551%	$100.2392	$100.24	$100.25	$100.20
Purchase #7	$189.44	11.786%	$211.7674	$211.77	$211.75	$211.80
7 purchase totals =	$908.23		$975.4595	$975.46	$975.40	$975.50