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	$103.34	5.500%	$109.0237	$109.02	$109.00	$109.00
Purchase #2	$156.61	7.595%	$168.5045	$168.50	$168.50	$168.50
Purchase #3	$69.69	3.281%	$71.9765	$71.98	$72.00	$72.00
Purchase #4	$246.32	6.556%	$262.4687	$262.47	$262.45	$262.50
Purchase #5	$6.29	11.571%	$7.0178	$7.02	$7.00	$7.00
Purchase #6	$78.26	13.752%	$89.0223	$89.02	$89.00	$89.00
Purchase #7	$220.40	13.125%	$249.3275	$249.33	$249.35	$249.30
7 purchase totals =	$880.91		$957.3410	$957.34	$957.30	$957.30