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	$171.69	6.454%	$182.7709	$182.77	$182.75	$182.80
Purchase #2	$97.92	6.150%	$103.9421	$103.94	$103.95	$103.90
Purchase #3	$61.94	8.656%	$67.3015	$67.30	$67.30	$67.30
Purchase #4	$111.91	6.623%	$119.3218	$119.32	$119.30	$119.30
Purchase #5	$45.88	12.612%	$51.6664	$51.67	$51.65	$51.70
Purchase #6	$96.95	3.292%	$100.1416	$100.14	$100.15	$100.10
Purchase #7	$248.38	8.120%	$268.5485	$268.55	$268.55	$268.50
7 purchase totals =	$834.67		$893.6928	$893.69	$893.65	$893.60