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	$145.57	3.814%	$151.122	$151.12	$151.10	$151.10
Purchase #2	$85.90	4.732%	$89.9648	$89.96	$89.95	$90.00
Purchase #3	$183.40	11.704%	$204.8651	$204.87	$204.85	$204.90
Purchase #4	$67.85	12.526%	$76.3489	$76.35	$76.35	$76.30
Purchase #5	$63.58	3.611%	$65.8759	$65.88	$65.90	$65.90
Purchase #6	$250.28	7.410%	$268.8257	$268.83	$268.85	$268.80
Purchase #7	$191.68	3.618%	$198.615	$198.62	$198.60	$198.60
7 purchase totals =	$988.26		$1,055.6174	$1,055.63	$1,055.60	$1,055.60