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	$41.98	9.331%	$45.8972	$45.90	$45.90	$45.90
Purchase #2	$88.52	7.800%	$95.4246	$95.42	$95.40	$95.40
Purchase #3	$237.88	3.279%	$245.6801	$245.68	$245.70	$245.70
Purchase #4	$131.27	4.282%	$136.891	$136.89	$136.90	$136.90
Purchase #5	$159.32	5.448%	$167.9998	$168.00	$168.00	$168.00
Purchase #6	$163.69	12.155%	$183.5865	$183.59	$183.60	$183.60
Purchase #7	$220.26	4.607%	$230.4074	$230.41	$230.40	$230.40
7 purchase totals =	$1,042.92		$1,105.8866	$1,105.89	$1,105.90	$1,105.90