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	$185.66	6.320%	$197.3937	$197.39	$197.40	$197.40
Purchase #2	$59.32	7.171%	$63.5738	$63.57	$63.55	$63.60
Purchase #3	$151.92	3.596%	$157.383	$157.38	$157.40	$157.40
Purchase #4	$173.35	3.170%	$178.8452	$178.85	$178.85	$178.80
Purchase #5	$205.78	4.510%	$215.0607	$215.06	$215.05	$215.10
Purchase #6	$168.87	3.302%	$174.4461	$174.45	$174.45	$174.40
Purchase #7	$165.59	12.279%	$185.9228	$185.92	$185.90	$185.90
7 purchase totals =	$1,110.49		$1,172.6253	$1,172.62	$1,172.60	$1,172.60