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	$140.43	8.376%	$152.1924	$152.19	$152.20	$152.20
Purchase #2	$171.36	8.791%	$186.4243	$186.42	$186.40	$186.40
Purchase #3	$47.32	12.497%	$53.2336	$53.23	$53.25	$53.20
Purchase #4	$86.91	5.498%	$91.6883	$91.69	$91.70	$91.70
Purchase #5	$37.98	13.603%	$43.1464	$43.15	$43.15	$43.10
Purchase #6	$176.92	6.171%	$187.8377	$187.84	$187.85	$187.80
Purchase #7	$73.39	12.447%	$82.5249	$82.52	$82.50	$82.50
7 purchase totals =	$734.31		$797.0476	$797.04	$797.05	$796.90