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	$30.26	11.138%	$33.6304	$33.63	$33.65	$33.60
Purchase #2	$54.83	9.143%	$59.8431	$59.84	$59.85	$59.80
Purchase #3	$88.85	6.296%	$94.444	$94.44	$94.45	$94.40
Purchase #4	$209.75	11.230%	$233.3049	$233.30	$233.30	$233.30
Purchase #5	$245.41	11.190%	$272.8714	$272.87	$272.85	$272.90
Purchase #6	$215.27	7.134%	$230.6274	$230.63	$230.65	$230.60
Purchase #7	$129.40	8.438%	$140.3188	$140.32	$140.30	$140.30
7 purchase totals =	$973.77		$1,065.0400	$1,065.03	$1,065.05	$1,064.90