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	$210.69	6.171%	$223.6917	$223.69	$223.70	$223.70
Purchase #2	$77.60	6.682%	$82.7852	$82.79	$82.80	$82.80
Purchase #3	$142.48	3.735%	$147.8016	$147.80	$147.80	$147.80
Purchase #4	$134.60	9.523%	$147.418	$147.42	$147.40	$147.40
Purchase #5	$64.26	12.207%	$72.1042	$72.10	$72.10	$72.10
Purchase #6	$31.41	7.768%	$33.8499	$33.85	$33.85	$33.80
Purchase #7	$85.48	4.637%	$89.4437	$89.44	$89.45	$89.40
7 purchase totals =	$746.52		$797.0943	$797.09	$797.10	$797.00