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	$51.70	11.700%	$57.7489	$57.75	$57.75	$57.70
Purchase #2	$129.86	4.653%	$135.9024	$135.90	$135.90	$135.90
Purchase #3	$198.47	6.166%	$210.7077	$210.71	$210.70	$210.70
Purchase #4	$232.72	7.625%	$250.4649	$250.46	$250.45	$250.50
Purchase #5	$105.84	11.654%	$118.1746	$118.17	$118.15	$118.20
Purchase #6	$168.53	11.448%	$187.8233	$187.82	$187.80	$187.80
Purchase #7	$85.76	4.215%	$89.3748	$89.37	$89.35	$89.40
7 purchase totals =	$972.88		$1,050.1966	$1,050.18	$1,050.10	$1,050.20