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	$43.69	3.217%	$45.0955	$45.10	$45.10	$45.10
Purchase #2	$238.56	9.614%	$261.4952	$261.50	$261.50	$261.50
Purchase #3	$190.36	10.181%	$209.7406	$209.74	$209.75	$209.70
Purchase #4	$107.87	3.250%	$111.3758	$111.38	$111.40	$111.40
Purchase #5	$155.34	4.681%	$162.6115	$162.61	$162.60	$162.60
Purchase #6	$152.41	9.603%	$167.0459	$167.05	$167.05	$167.00
Purchase #7	$110.88	11.474%	$123.6024	$123.60	$123.60	$123.60
7 purchase totals =	$999.11		$1,080.9669	$1,080.98	$1,081.00	$1,080.90