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	$176.60	9.463%	$193.3117	$193.31	$193.30	$193.30
Purchase #2	$201.40	4.390%	$210.2415	$210.24	$210.25	$210.20
Purchase #3	$6.72	4.725%	$7.0375	$7.04	$7.05	$7.00
Purchase #4	$240.60	9.784%	$264.1403	$264.14	$264.15	$264.10
Purchase #5	$67.61	9.494%	$74.0289	$74.03	$74.05	$74.00
Purchase #6	$173.52	13.363%	$196.7075	$196.71	$196.70	$196.70
Purchase #7	$63.73	13.553%	$72.3673	$72.37	$72.35	$72.40
7 purchase totals =	$930.18		$1,017.8347	$1,017.84	$1,017.85	$1,017.70