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	$182.43	6.543%	$194.3664	$194.37	$194.35	$194.40
Purchase #2	$126.27	3.673%	$130.9079	$130.91	$130.90	$130.90
Purchase #3	$107.77	6.526%	$114.8031	$114.80	$114.80	$114.80
Purchase #4	$236.67	11.236%	$263.2622	$263.26	$263.25	$263.30
Purchase #5	$156.30	5.470%	$164.8496	$164.85	$164.85	$164.80
Purchase #6	$79.41	13.154%	$89.8556	$89.86	$89.85	$89.90
Purchase #7	$146.68	10.616%	$162.2515	$162.25	$162.25	$162.30
7 purchase totals =	$1,035.53		$1,120.2963	$1,120.30	$1,120.25	$1,120.40