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	$64.44	9.865%	$70.797	$70.80	$70.80	$70.80
Purchase #2	$127.50	11.844%	$142.6011	$142.60	$142.60	$142.60
Purchase #3	$70.57	9.682%	$77.4026	$77.40	$77.40	$77.40
Purchase #4	$232.60	7.689%	$250.4846	$250.48	$250.50	$250.50
Purchase #5	$162.27	12.864%	$183.1444	$183.14	$183.15	$183.10
Purchase #6	$153.80	5.484%	$162.2344	$162.23	$162.25	$162.20
Purchase #7	$247.33	7.384%	$265.5928	$265.59	$265.60	$265.60
7 purchase totals =	$1,058.51		$1,152.2569	$1,152.24	$1,152.30	$1,152.20