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	$106.90	9.335%	$116.8791	$116.88	$116.90	$116.90
Purchase #2	$83.67	9.717%	$91.8002	$91.80	$91.80	$91.80
Purchase #3	$185.33	13.816%	$210.9352	$210.94	$210.95	$210.90
Purchase #4	$89.68	9.629%	$98.3153	$98.32	$98.30	$98.30
Purchase #5	$170.76	6.746%	$182.2795	$182.28	$182.30	$182.30
Purchase #6	$114.59	3.655%	$118.7783	$118.78	$118.80	$118.80
Purchase #7	$126.90	3.582%	$131.4456	$131.45	$131.45	$131.40
7 purchase totals =	$877.83		$950.4332	$950.45	$950.50	$950.40