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	$95.33	5.664%	$100.7295	$100.73	$100.75	$100.70
Purchase #2	$85.57	12.597%	$96.3493	$96.35	$96.35	$96.30
Purchase #3	$25.79	12.250%	$28.9493	$28.95	$28.95	$28.90
Purchase #4	$89.84	10.717%	$99.4682	$99.47	$99.45	$99.50
Purchase #5	$164.27	5.471%	$173.2572	$173.26	$173.25	$173.30
Purchase #6	$101.54	5.691%	$107.3186	$107.32	$107.30	$107.30
Purchase #7	$94.77	12.144%	$106.2789	$106.28	$106.30	$106.30
7 purchase totals =	$657.11		$712.3510	$712.36	$712.35	$712.30