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	$229.50	9.223%	$250.6668	$250.67	$250.65	$250.70
Purchase #2	$174.30	4.672%	$182.4433	$182.44	$182.45	$182.40
Purchase #3	$5.41	7.241%	$5.8017	$5.80	$5.80	$5.80
Purchase #4	$185.25	6.328%	$196.9726	$196.97	$196.95	$197.00
Purchase #5	$69.90	12.797%	$78.8451	$78.85	$78.85	$78.80
Purchase #6	$242.88	10.640%	$268.7224	$268.72	$268.70	$268.70
Purchase #7	$112.36	13.299%	$127.3028	$127.30	$127.30	$127.30
7 purchase totals =	$1,019.60		$1,110.7547	$1,110.75	$1,110.70	$1,110.70