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	$212.45	3.131%	$219.1018	$219.10	$219.10	$219.10
Purchase #2	$76.94	5.127%	$80.8847	$80.88	$80.90	$80.90
Purchase #3	$159.75	3.478%	$165.3061	$165.31	$165.30	$165.30
Purchase #4	$48.88	3.266%	$50.4764	$50.48	$50.50	$50.50
Purchase #5	$170.68	9.834%	$187.4647	$187.46	$187.45	$187.50
Purchase #6	$250.36	12.531%	$281.7326	$281.73	$281.75	$281.70
Purchase #7	$161.91	3.440%	$167.4797	$167.48	$167.50	$167.50
7 purchase totals =	$1,080.97		$1,152.4460	$1,152.44	$1,152.50	$1,152.50