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	$127.93	5.424%	$134.8689	$134.87	$134.85	$134.90
Purchase #2	$33.54	11.279%	$37.323	$37.32	$37.30	$37.30
Purchase #3	$169.93	6.293%	$180.6237	$180.62	$180.60	$180.60
Purchase #4	$10.51	7.731%	$11.3225	$11.32	$11.30	$11.30
Purchase #5	$186.44	5.361%	$196.435	$196.44	$196.45	$196.40
Purchase #6	$139.31	10.621%	$154.1061	$154.11	$154.10	$154.10
Purchase #7	$71.67	3.687%	$74.3125	$74.31	$74.30	$74.30
7 purchase totals =	$739.33		$788.9917	$788.99	$788.90	$788.90