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	$86.92	4.662%	$90.9722	$90.97	$90.95	$91.00
Purchase #2	$127.62	10.461%	$140.9703	$140.97	$140.95	$141.00
Purchase #3	$240.65	11.736%	$268.8927	$268.89	$268.90	$268.90
Purchase #4	$96.84	7.437%	$104.042	$104.04	$104.05	$104.00
Purchase #5	$220.54	10.669%	$244.0694	$244.07	$244.05	$244.10
Purchase #6	$188.51	12.421%	$211.9248	$211.92	$211.90	$211.90
Purchase #7	$218.89	9.698%	$240.118	$240.12	$240.10	$240.10
7 purchase totals =	$1,179.97		$1,300.9894	$1,300.98	$1,300.90	$1,301.00